Electrical muscle stimulation

Abstract

A method for providing a plyometric exercise to a subject, including: selecting at least one target region of interest (RO I) in a subject body for a plyometric exercise; positioning at least 2 electrodes above a tissue volume at the selected target ROI; generating at least one electric field by at least one pulse generator electrically coupled to the at least 2 electrodes; delivering the at least one electric field between the at least 2 electrodes to the tissue volume with parameter values selected for contracting at least one muscle in the tissue volume as part of a plyometric exercise of the at least one muscle.

Description

RELATED APPLICATION / S This application claims the benefit of priority under 35 USC § 119(e) of U.S. Provisional Patent Application No. 63 / 618,429 filed January 08, 2024, the contents of which are incorporated herein by reference in their entirety. FIELD AND BACKGROUND OF THE INVENTION The present invention, in some embodiments thereof, relates to stimulation of muscles and, more particularly, but not exclusively, to electrical stimulation of muscles. International Patent Application Publication No. WO2021117047A1 describes, “a system for stimulating a muscle of a user, the system comprising: a stimulating unit comprising (i) at least two electrodes configured to be placed in electrical contact with skin of a user in a vicinity of the muscle, and (ii) a pulse generator configured to generate an electrical pulse for application to the muscle through the at least two electrodes; a sensing unit comprising at least one sensor configured to measure a physiological parameter of the user and generate a sensing signal in response thereto; and a control processor operatively coupled to the stimulating unit and to the sensing unit and configured to receive the sensing signal from the at least one sensor and change a parameter of the electrical pulse applied by the at least two electrodes in response to the sensing signal” (abstract). SUMMARY OF THE INVENTION Some examples of some embodiments of the invention are listed below (an embodiment may include features from more than one example and / or fewer than all features of an example): Example 1. A method for providing a plyometric exercise to a subject, comprising: selecting at least one target region of interest (ROI) in a subject body for a plyometric exercise; positioning at least 2 electrodes above a tissue volume at the selected target ROI; generating at least one electric field by at least one pulse generator electrically coupled to the at least 2 electrodes; delivering the at least one electric field between the at least 2 electrodes to the tissue volume with parameter values selected for contracting at least one muscle in the tissue volume as part of a plyometric exercise of the at least one muscle. 2 Example 2. A method according to example 1, wherein the delivering comprises delivering the at least one electric field with parameter values selected for inducing rapid movement between contraction and relaxation of the at least one muscle. Example 3. A method according to any one of examples 1 or 2, wherein the delivering comprises delivering short repetitive bursts of the at least one electric field between the at least 2 electrodes and into the tissue volume, wherein each burst of the short repetitive bursts lasts for up to 4 seconds, and wherein an interval between two consecutive short repetitive bursts is up to 8 seconds. Example 4. A method according to any one of the previous examples, wherein the selecting comprises selecting at least two spaced apart region of interests (ROIs) in a subject body for a plyometric exercise, wherein the positioning comprises positioning at least two pairs of electrodes, each above a tissue volume at a different ROI of the at least two spaced apart ROIs, and wherein the delivering comprises delivering a first electric field between a first pair of electrodes of the at least two pairs of electrodes, and a second electric field between a second pair of electrodes of the at least two pairs of electrodes, in synchronization with the delivery of the first electric field, according to predetermined timing. Example 5. A method according to example 4, wherein the predetermined timing is selected for contracting in parallel or in a sequence at least one first muscle in a tissue volume of a first ROI of the at least two spaced apart region of interests (ROIs) by the first electric field, and at least one second muscle in a different tissue volume of a second ROI by the second electric field. Example 6. A method according to any one of examples 4 or 5, wherein each of the at least two spaced apart region of interests (ROIs) is located at a different side of a body midline or in a same side of the body midline. Example 7. A method according to any one of examples 4 to 6, wherein each of the at least two spaced apart ROIs is located above the waist line or below the waist line. Example 8. A method according to any one of examples 4 to 6, wherein at least one first ROI of the at least two spaced apart ROIs is located above the waist line, and at least one second ROI of the at least two spaced apart ROIs is located below the waist line. Example 9. A method according to example 8, wherein the at least one first ROI comprises an abdomen region or buttock region, and wherein the at least one second ROI comprises a leg region. Example 10. A method according to any one of the previous examples, wherein the positioning the at least 2 electrodes comprise positioning at least 3 electrodes above the tissue volume at the selected target ROI, and wherein the delivering comprises delivering the at least one electric 3 field intermittently between at least two pairs of the at least 3 electrodes using at least one shared electrode of the at least 3 electrodes. Example 11. A method according to any one of the previous examples, wherein the generating comprises generating the at least one electric field with a frequency of at least 25Hz and with an intensity between 10mA and 80mA. Example 12. A method for delivery of a muscle stimulation training, comprising: selecting at least one target region of interest (ROI) in a subject body for the muscle stimulation training; positioning at least 3 electrodes on a surface of a tissue volume at the selected target ROI; delivering at least one electric field intermittently between at least two pairs of the at least 3 electrodes to the tissue volume, with parameter values suitable for simultaneous contraction of at least 2 muscles in the tissue volume. Example 13. A method according to example 12, wherein the positioning comprises positioning the at least 3 electrodes at a distance relative to each other suitable for generating contraction of muscles in at least two different directions by the at least one electric field, wherein an angle between the at least two directions is between 10 degrees and 180 degrees. Example 14. A method according to any one of examples 12 and 13, comprising: generating the at least one electric field by at least one pulse generator electrically coupled to the at least 3 electrodes. Example 15. A method according to example 14, wherein the at least one electric field is generated with a frequency of at least 50 Hz, and wherein an electric field delivered between each pair of electrodes of the at least two pairs has a frequency of at least 25 Hz, and a pulse width between 100 ps and 1150 ps. Example 16. A method according to any one of the previous examples, wherein the at least one electric field has an intensity between 10mA and 80mA. Example 17. A method according to any one of examples 12 to 16, wherein the delivering comprises delivering the at least one electric field intermittently between the at least two pairs of the at last 3 electrodes during a time period between 2 seconds and 60 minutes. Example 18. A method according to any one of examples 12 to 17, wherein the positioning the at least 3 electrodes comprises positioning at least 4 electrodes on the surface of the tissue volume at the selected target ROI, and wherein the delivering the at least one electric field comprises delivering at least one first electric field intermittently between a first set of two electrode pairs of the at least 4 electrodes, and delivering at least one second electric field 4 intermittently between a second different set of two electrode pairs of the at least 4 electrodes having a shared electrode when the delivering of the at least one first electric field is stopped. Example 19. A method for delivery of a muscle stimulation training, comprising: selecting at least one target region of interest (ROI) in a subject body for the muscle stimulation training; positioning at least 3 electrodes on a surface of a tissue volume at the selected target ROI; delivering at least one electric field between at least 3 pairs of the at least 3 electrodes to the tissue volume, with parameter values suitable for contraction of at least 2 different muscles in the tissue volume, wherein a duration of the delivering is between 10 minutes and 40 minutes, and wherein the delivering is performed while the at least 3 electrodes remain coupled directly or indirectly to the tissue surface during the delivering time. Example 20. A method according to example 19, comprising: generating the at least one electric field by at least one pulse generator electrically coupled to the at least 3 electrodes. Example 21. A method according to example 20, wherein the at least one electric field is generated with a frequency of at least 50 Hz, and wherein an electric field delivered between each pair of electrodes of the at least two pairs has a frequency of at least 25 Hz, and a pulse width between 100 ps and 1150 ps. Example 22. A method according to any one of examples 20 or 21, wherein the at least one electric field has an intensity between 10mA and 80mA. Example 23. A method according to any one of examples 19 to 22, wherein the selecting comprises selecting at least one first ROI and at least one second ROI, wherein the positioning comprising positioning at least one 3 electrodes of at least one first stimulation module on a surface of a tissue volume at the at least one first ROI, and at least one 3 electrodes of at least one second stimulation module on a surface of a tissue volume at the at least one second ROI; and wherein the delivering comprises delivering electric fields by the at least one first stimulation module and the at least one second stimulation module, in synchronization with timing parameters suitable for generating simultaneous or sequential contraction of muscles in the at least one first ROI and muscles in the at the at least one second ROI. Example 24. A method according to example 23, wherein the at least one first ROI and the at least one second ROI are located at an upper body portion of a subject above a waist line, at a same side of the body midline or at opposite sides of the body midline. 5 Example 25. A method according to example 23, wherein the at least one first ROI and the at least one second ROI are located at a lower body portion of a subject below a waist line, at a same side of the body midline or at opposite sides of the body midline. Example 26. A method according to example 23, wherein the at least one first ROI is located above the waist line and the at least one second ROI is located below the waist line. Example 27. A method according to example 26, wherein the at least one first ROI comprises an abdomen region, and wherein the at least one second ROI comprises a leg region. Example 28. A stimulation module, comprising: at least 3 electrodes configured to be coupled directly or indirectly to a skin surface of a subject at a distance from each other, and wherein the at least 3 electrodes are configured to deliver an electric field transcutanously to at least one tissue volume beneath the skin surface; a pulse generator configured to generate at least one electric field, wherein the pulse generator is electrically connected to each of the at least 3 electrodes; a memory circuitry configured to store electric field parameter values; a control circuitry, wherein the control circuitry signals the pulse generator to generate at least one electric field based on parameter values stored in the memory and to deliver the electric field intermittently to at least 2 electrode pairs of the at least 3 electrodes with parameter values suitable for contracting simultaneously at least two muscles in the at least one tissue volume. Example 29. A stimulation module according to example 28, wherein a frequency of a portion of the at least one electric field delivered between each pair of the at least 2 electrode pairs is between 25 Hz and 100 Hz. Example 30. A stimulation module according to any one of examples 28 or 29, wherein the at least one electric field is delivered with an intensity between 10 mA - 60 mA. Example 31. A stimulation module according to any one of examples 28 to 30, comprising at least one multiplexer module configured to direct the at least one electric field generated by the pulse generator to the at least 2 electrode pairs. Example 32. A stimulation module according to any one of examples 28 to 31, wherein the at least 3 electrodes are configured to be reversibly coupled to one or more electrode pads by magnetic coupling. Example 33. A stimulation module according to any one of examples 28 to 32, comprising a communication circuitry configured to communicate with at least one remote device. Example 34. A stimulation module according to example 33, wherein the stimulation module is programmed based on signals received by the communication circuitry. 6 Example 35. A stimulation module according to any one of examples 33 or 34, wherein the communication circuitry is configured to communicate with the at least one remote device using wireless signals. Example 36. A stimulation module according to any one of examples 28 to 35, comprising at least one battery, wherein the at least one battery is a rechargeable and / or a replaceable battery. Example 37. A stimulation module according to example 36, comprising at least one set of charging conductors for reversibly electrically coupling the at least one battery to an external power source. Example 38. A stimulation module according to any one of examples 28 to 37, comprising at least one user interface for generating a human detectable indication with information about activity and / or position of the stimulation module and / or position of one or more of the at least 3 electrodes. Example 39. A stimulation module according to example 38, comprising at least one position detector for detecting a position of the stimulation module and / or a position of the at least 3 electrodes on a subject body, and wherein the at least one user interface generates the human detectable indication based on a signal received from the at least one detector with information about the detected position. Example 40. A stimulation module according to any one of examples 28 to 39, wherein the memory stores at least one electrical muscle stimulation (EMS) training protocol, and wherein the control circuitry signals the pulse generator to generate the at least one electric field according to the at least one EMS training protocol. Example 41. A stimulation module, comprising: at least 3 electrodes configured to be coupled directly or indirectly to a skin surface of a subject at a distance from each other, and wherein the at least 3 electrodes are configured to deliver an electric field transcutanously to at least one tissue volume beneath the skin surface; a pulse generator configured to generate at least one electric field, wherein the pulse generator is electrically connected to each of the at least 3 electrodes; a memory circuitry configured to store electric field parameter values; a control circuitry, wherein the control circuitry signals the pulse generator to generate the at least one electric field based on parameter values stored in the memory and to deliver the at least one electric field sequentially and / or intermittently between at least 3 electrode pairs of the at least 3 electrodes while the at least 3 electrodes remain stationary coupled to the skin surface, wherein the at least one electric field is delivered to the at least 3 electrode pairs with parameter values suitable for contracting at least two muscles in the at least one tissue volume. 7 Example 42. A stimulation module according to example 41, wherein the at least one electric field is delivered to the at least 3 electrode pairs during a time period stored in the memory, wherein the time period is between 10 minutes and 50 minutes stored in the memory. Example 43. A stimulation module according to any one of examples 41 or 42, wherein the at least one electric field is delivered with a frequency between 25 Hz and 100 Hz. Example 44. A stimulation module according to any one of examples 41 to 43, wherein the at least one electric field is delivered with an intensity between 10 mA - 60 mA. Example 45. A stimulation module according to any one of examples 41 to 44, comprising at least one multiplexer module configured to direct the at least one electric field generated by the pulse generator to the at least 3 electrode pairs. Example 46. A stimulation module according to any one of examples 41 to 45, comprising a communication circuitry configured to communicate with at least one remote device. Example 47. A stimulation module according to example 46, wherein the stimulation module is programmed based on signals received by the communication circuitry. Example 48. A stimulation module according to any one of examples 46 or 47, wherein the communication circuitry is configured to communicate with the at least one remote device using wireless signals. Example 49. A stimulation module according to any one of examples 41 to 48, wherein the memory stores at least one electrical muscle stimulation (EMS) training protocol, and wherein the control circuitry signals the pulse generator to generate the at least one electric field according to the at least one EMS training protocol. Example 50. A system for delivery of electrical muscle stimulation (EMS), comprising: at least 2 stimulation modules, each comprises: at least 3 electrodes, configured to be coupled to a tissue surface at a distance from each other; at least one pulse generator electrically connected to each of the at least 3 electrodes, configured to generate at least one electric field and to deliver the at least one electric field between at least 2 pairs of the at least 3 electrodes to at least one tissue volume underneath the tissue surface; a control circuitry, wherein the control circuitry is configured to signal the at least one pulse generator to generate and deliver the at least one electric field in synchronization between the at least 2 pairs or electrodes; at least one battery electrically connected to the control circuitry; a communication circuitry; wherein the at least 2 stimulation modules are configured to be coupled to a subject body at spaced-apart target locations; 8 a control console, comprising: a user interface configured to generate a human detectable indication; a memory circuitry storing at least one stimulation protocol or indications thereof; a communication circuitry configured to communicate with each of the at least 2 stimulation modules; a control circuitry, wherein the control circuitry signals each of the at least 2 stimulation modules using the control console communication circuitry to generate and deliver electric fields to tissue volumes at the spaced-apart target locations with parameter values suitable for contracting muscles in the tissue volumes simultaneously or sequentially, according to the at least one stimulation protocol or indications thereof stored in the memory. Example 51. A system according to example 50, wherein the control circuitry of the control console signals each of the at least 2 stimulation modules to deliver the at least one electric field, during a time period between 10 minutes and 40 minutes while the at least 2 stimulation modules remain coupled to the tissue surface at the spaced-apart target locations. Example 52. A system according to any one of examples 50 or 51, wherein the control console communicates with each of the at least 2 stimulation modules by wireless communication. Example 53. A system according to example 52, wherein the control console user interface generates the human detectable indication with information about an activation status of each of the at least 2 stimulation modules. Example 54.  A system according to any one of examples 50 to 53, wherein the control console user interface generates the human detectable indication with information about an electrical power level in the at least one battery of each of the at least 2 stimulation modules. Example 55.  A system according to any one of examples 50 to 54, wherein the control console user interface is configured to receive at least one input signal with information about at least one of, electric field intensity, electric field frequency and timing values for delivery of an electric field by one or both of the at least 2 stimulation modules, and wherein the control console is used for programming one or both of the at least 2 stimulation modules based on the at least one input signal. Example 56. A system according to any one of examples 50 to 55, wherein each of the at least 2 stimulation modules comprise at least one position detector configured to detect a position of a stimulation module or a position of each of the at least 3 electrodes of the stimulation module. Example 57. A system according to example 56, wherein each of the at least 2 stimulation modules comprise a user interface configured to generate a visual indication with information 9 about a position of a stimulation module or a position of each of the at least 3 electrodes of the stimulation module, based on information received from the at least one position detector. Example 58. A system according to any one of examples 50 to 56, wherein each of the at least 2 stimulation modules comprise a user interface configured to generate a visual indication that match a visual indication generated by the control console user interface. Example 59. A system according to example 58, wherein the visual indication generated by a user interface of each of the at least 2 stimulation modules is a color coded visual indication. Example 60. A system according to any one of examples 50 to 59, wherein a pulse generator of each of the at least 2 stimulation modules generates the at least one electric field with a frequency between 25 Hz and 100 Hz. Example 61. A system according to any one of examples 50 to 60, wherein a pulse generator of each of the at least 2 stimulation modules generates the at least one electric field with intensity between 10 mA and 80 mA. Example 62. A system according to any one of examples 50 to 61, wherein a pulse generator of each of the at least 2 stimulation modules repeatedly generates the at least one electric field for a time period between 2 seconds and 12 second with intervals between 1 second and 10 seconds. Example 63. A system according to any one of examples 50 to 62, wherein each of the at least 2 stimulation modules comprises electrical charging conductors, electrically coupled to the at least one battery, wherein the electrical charging conductors are configured to electrically couple the at least one battery to an external power source. Example 64. An electrode unit, comprising: a housing having a tissue contacting surface configured to be placed in contact directly or indirectly with a tissue surface; at least one electrode within the housing, wherein the electrode comprises an electric connector for connecting the electrode to an external power source; at least one magnetic connector configured to reversibly magnetically couple the at least one electrode to at least one electrical conductor of at least one electrode pad. Example 65. An electrode unit according to example 64, wherein the at least one magnetic connector comprises at least one magnet configured to apply a magnetic field on at least a portion of the at least one electrical conductor. Example 66. An electrode unit according to any one of examples 64 or 65, wherein the at least one magnetic connector comprises at least two spaced apart magnetic connectors configured to reversibly couple the at least one electrode to the at least one electrical conductor of the at least one electrode pad. 10 Example 67. An electrode unit according to example 66, wherein a distance between the at least two spaced apart magnetic connectors is between 1 cm and 12 cm. Example 68. An electrode unit according to any one of examples 66 or 67, wherein the at least one electrode comprises at least two electrodes, and wherein each of the at least two spaced apart magnetic connectors is configured to couple at least one electrode of the at least two electrodes to a different electrical connector of the at least one electrode pad. Example 69. An electrode unit according to any one of examples 64 to 68, wherein the at least one magnetic connector comprises an opening shaped and sized to receive a portion of the at least one electrical conductor. Example 70. An electrode pad, comprising: a body having a first surface and a second tissue contacting surface coated with an adhesive coating configured to attach the tissue contacting surface to a surface of a tissue: at least two spaced apart electrical conductors crossing through the body between the second tissue contacting surface and the first surface, and extend through the first surface; wherein the at least two spaced apart electrical conductors are configured to conduct electricity through the electrode pad body to a tissue contacting the tissue contacting surface or the adhesive coating. Example 71. An electrode pad according to example 70, wherein a distance between the at least two spaced apart electrical conductors is between 1 cm and 20 cm. Example 72. An electrode pad according to any one of examples 70 or 71, wherein the electrode pad body is flexible to conform to anatomy of the tissue surface. Example 73. An electrode pad according to any one of examples 70 to 72, wherein a thickness of the electrode pad body is between 0.5 mm and 5 mm. Example 74. An electrode pad according to any one of examples 70 to 73, wherein a surface area of the tissue contacting surface of the electrode pad body is between 15cm2 and 50cm2. Example 75. A charging module, comprising: a body comprising: a plurality of charging slots shaped as pockets arranged side by side in the body, wherein each charging slot is shaped and sized to receive electrodes of a stimulation module via an opening of the charging slot while keeping a control unit comprising a user interface and charging connectors of the stimulation module outside the charging slot; a plurality of pairs of charging connectors, wherein each pair of the charging connectors is positioned in the body above each opening, and is aligned with the opening; a base configured to allow placing of the charging module on a surface. 11 Example 76. A charging module according to example 75, comprising a plurality of magnetic connectors, each is adjacent to a pair of the charging connectors, wherein each of the plurality of magnetic connectors is configured to magnetically couple the control unit to the body while electrically coupling the control unit charging connectors to the pair of the charging connectors. 5 Example 77. A charging module according to example 75, wherein each pair of the charging connectors of the charging module comprises at least one magnetic connector configured to magnetically couple the control unit to the body while electrically coupling the control unit charging connectors to the pair of the charging connectors. Example 78. A charging module according to any one of examples 75 to 77, wherein a width 10 of each opening of a charging slot is between 5 cm and 15 cm. Additional examples of some embodiments of the invention are listed below (an embodiment may include features from more than one example and / or fewer than all features of an example): Example 1. A method for providing a plyometric exercise to a subject, comprising: selecting at least one target region of interest (ROI) in a subject body for a plyometric exercise; positioning at least 2 electrodes above a tissue volume at the selected target ROI; generating at least one electric field by at least one pulse generator electrically coupled to the at least 2 electrodes; delivering the at least one electric field between the at least 2 electrodes to the tissue volume with parameter values selected for contracting at least one muscle in the tissue volume as part of a plyometric exercise of the at least one muscle. Example 2. A method according to example 1, wherein the delivering comprises delivering the at least one electric field with parameter values selected for inducing rapid movement between contraction and relaxation of the at least one muscle. Example 3. A method according to any one of examples 1 or 2, wherein the delivering comprises delivering short repetitive bursts of the at least one electric field between the at least 2 electrodes and into the tissue volume, wherein each burst of the short repetitive bursts lasts for up to 4 seconds, and wherein an interval between two consecutive short repetitive bursts is up to 8 seconds. Example 4. A method according to any one of the previous examples, wherein the selecting comprises selecting at least two spaced apart region of interests (ROIs) in a subject body for a plyometric exercise, wherein the positioning comprises positioning at least two pairs of electrodes, each above a tissue volume at a different ROI of the at least two spaced apart ROIs, and wherein the delivering comprises delivering a first electric field between a first pair of 12 electrodes of the at least two pairs of electrodes, and a second electric field between a second pair of electrodes of the at least two pairs of electrodes, in synchronization with the delivery of the first electric field, according to predetermined timing. Example 5. A method according to example 4, wherein the predetermined timing is selected for contracting in parallel or in a sequence at least one first muscle in a tissue volume of a first ROI of the at least two spaced apart region of interests (ROIs) by the first electric field, and at least one second muscle in a different tissue volume of a second ROI by the second electric field. Example 6. A method according to any one of examples 4 or 5, wherein each of the at least two spaced apart region of interests (ROIs) is located at a different side of a body midline or in a same side of the body midline. Example 7. A method according to any one of examples 4 to 6, wherein each of the at least two spaced apart ROIs is located above the waist line or below the waist line. Example 8. A method according to any one of examples 4 to 6, wherein at least one first ROI of the at least two spaced apart ROIs is located above the waist line, and at least one second ROI of the at least two spaced apart ROIs is located below the waist line. Example 9. A method according to example 8, wherein the at least one first ROI comprises an arm region, and upper back region, a lower back region, and / or an abdomen region, and wherein the at least one second ROI comprises a leg region. Example 10. A method according to any one of the previous examples, wherein the positioning the at least 2 electrodes comprises positioning at least 3 electrodes above the tissue volume at the selected target ROI, and wherein the delivering comprises delivering the at least one electric field intermittently between at least two pairs of the at least 3 electrodes using at least one shared electrode of the at least 3 electrodes. Example 11. A method according to any one of the previous examples, wherein the generating comprises generating the at least one electric field with a frequency of at least 25Hz and with an intensity between 10mA and 80mA. Example 12. A method for delivery of an electric muscle stimulation training, comprising: selecting at least one target region of interest (ROI) in a subject body for the muscle stimulation training; positioning at least 3 electrodes on a surface of a tissue volume at the selected at least one target ROI; generating at least on electric field with parameter values suitable to contract at least one muscle in the tissue volume; 13 delivering the at least on electric field intermittently between at least 2 pairs of the at least 3 electrodes to the tissue volume, with timing values suitable for simultaneous contraction of at least 2 muscles in the tissue volume. Example 13. A method according to example 12, wherein the positioning comprises positioning the at least 3 electrodes at a distance relative to each other suitable for generating contraction of muscles in at least two different directions by the at least one electric field, wherein an angle between the at least two directions is between 10 degrees and 180 degrees. Example 14. A method according to any one of examples 12 or 13, wherein the generating comprises generating the at least one electric field with a phase duration of between 50 ps and 500 ps, and with frequency between 1Hz and 150Hz. Example 15. A method according to any one of examples 12 or 13, comprising: generating the at least one electric field by at least one pulse generator electrically coupled to the at least 3 electrodes and positioned on the subject body. Example 16. A method according to example 15, wherein the at least one electric field is generated with a frequency of at least 50 Hz, and wherein an electric field delivered between each pair of electrodes of the at least two pairs has a frequency of at least 25 Hz, and a pulse width between 100 ps and 1150 ps. Example 17. A method according to any one of examples 12 to 16, wherein the at least one electric field has an intensity between 10mA and 80mA. Example 18. A method according to any one of examples 12 to 17, wherein the delivering comprises delivering the at least one electric field intermittently between the at least two pairs of the at last 3 electrodes during a time period between 2 seconds and 60 minutes. Example 19. A method according to any one of examples 12 to 18, wherein the positioning the at least 3 electrodes comprises positioning at least 4 electrodes on the surface of the tissue volume at the selected at least one target ROI, and wherein the delivering the at least one electric field comprises delivering at least one first electric field intermittently between a first set of two electrode pairs of the at least 4 electrodes, and delivering at least one second electric field intermittently between a second different set of two electrode pairs of the at least 4 electrodes having a shared electrode when the delivering of the at least one first electric field is stopped. Example 20. A method according to any one of examples 12 to 19, wherein the selected at least one target ROI comprises at least one of, a calf region of a leg, upper back, lower back and abdomen. Example 21. A method for delivery of a muscle stimulation training, comprising: 14 selecting at least one target region of interest (ROI) in a subject body for the muscle stimulation training; positioning at least 3 electrodes on a surface of a tissue volume at the selected at least one target ROI; generating at least one electric field, with parameter values suitable to contract at least one muscle in the tissue volume; delivering the at least one electric field, between at least 2 pairs of the at least 3 electrodes to the tissue volume, with parameter values suitable for contraction of at least 2 different muscles in the tissue volume, wherein a duration of the delivering is between 2 minutes and 60 minutes, and wherein the delivering is performed while the at least 3 electrodes remain coupled directly or indirectly to the tissue surface during the delivering time. Example 22. A method according to example 21, wherein the at least one target ROI comprises, at least one arm, at least one leg, an abdomen, buttocks, upper back, and / or lower back. Example 23. A method according to any one of examples 21 or 22, wherein the generating comprises generating the at least one electric field by at least one pulse generator electrically coupled to the at least 3 electrodes, and positioned on the subject body. Example 24. A method according to any one of examples 21 to 23, wherein the generating comprises generating the at least one electric field as a biphasic pulse having a plus phase and a minus phase, each with a phase duration of between 100 ps and 500 ps, and with frequency between 1Hz and 150Hz. Example 25. A method according to any one of examples 21 to 23, wherein the at least one electric field is generated with a frequency of at least 2 Hz, and wherein an electric field delivered between each pair of electrodes of the at least two pairs has a frequency of at least 1 Hz, and a pulse width between 100 ps and 1150 ps. Example 26. A method according to any one of examples 21 to 25, wherein the generating comprises generating the at least one electric field with an intensity between 10mA and 80mA. Example 27. A method according to any one of examples 21 to 26, wherein the selecting comprises selecting at least one first ROI and at least one second ROI, wherein the positioning comprising positioning at least 3 electrodes of at least one first stimulation module on a surface of a tissue volume at the at least one first ROI, and at least 3 electrodes of at least one second stimulation module on a surface of a tissue volume at the at least one second ROI; and wherein the delivering comprises delivering electric fields by the at least one first stimulation module and the at least one second stimulation module, in synchronization with 15 timing parameters suitable for generating simultaneous or sequential contraction of muscles in the at least one first ROI and muscles in the at the at least one second ROI. Example 28. A method according to example 27, wherein the at least one first ROI and the at least one second ROI are located at an upper body portion of a subject above a waist line, at a same side of the body midline or at opposite sides of the body midline. Example 29. A method according to example 27, wherein the at least one first ROI and the at least one second ROI are located at a lower body portion of a subject below a waist line, at a same side of the body midline or at opposite sides of the body midline. Example 30. A method according to example 27, wherein the at least one first ROI is located above the waist line and the at least one second ROI is located below the waist line. Example 31. A method according to example 30, wherein the at least one first ROI comprises an abdomen region, and wherein the at least one second ROI comprises a leg region. Example 32. A stimulation module, comprising: at least 3 electrodes configured to be coupled directly or indirectly to a skin surface of a subject at a distance from each other, and wherein the at least 3 electrodes are configured to deliver an electric field transcutanously to at least one tissue volume beneath the skin surface; a pulse generator configured to generate at least one electric field, wherein the pulse generator is electrically connected to each of the at least 3 electrodes; a memory circuitry configured to store electric field parameter values; a control circuitry, wherein the control circuitry signals the pulse generator to generate at least one electric field based on parameter values stored in the memory and to deliver the electric field sequentially or intermittently to at least 2 electrode pairs of the at least 3 electrodes with parameter values suitable for contracting simultaneously at least two muscles in the at least one tissue volume. Example 33. A stimulation module according to example 32, wherein a frequency of a portion of the at least one electric field delivered between each pair of the at least 2 electrode pairs is between 25 Hz and 100 Hz. Example 34. A stimulation module according to any one of examples 32 or 33, wherein the at least one electric field is delivered with an intensity between 10 mA - 60 mA. Example 35. A stimulation module according to any one of examples 32 to 34, comprising at least one multiplexer module configured to direct the at least one electric field generated by the pulse generator to the at least 2 electrode pairs. 16 Example 36. A stimulation module according to any one of examples 32 to 35, wherein the at least 3 electrodes are configured to be reversibly coupled to one or more electrode pads by magnetic coupling. Example 37. A stimulation module according to any one of examples 32 to 36, comprising a communication circuitry configured to communicate with at least one remote device. Example 38. A stimulation module according to example 37, wherein the stimulation module is programmed based on signals received by the communication circuitry. Example 39. A stimulation module according to any one of examples 37 or 38, wherein the communication circuitry is configured to communicate with the at least one remote device using wireless signals. Example 40. A stimulation module according to any one of examples 32 to 39, comprising at least one battery, wherein the at least one battery is a rechargeable and / or a replaceable battery. Example 41. A stimulation module according to any one of examples 32 to 40, comprising at least one detector configured to detect signals indicating muscle fatigue, and wherein the control circuitry controls generation of the at least one electric field based on the detected signals received from the at least one detector. Example 42. A system for delivery of electrical muscle stimulation (EMS), comprising: at least one stimulation module, comprising: at least 3 electrodes, configured to be coupled to a tissue surface at a distance from each other; at least one pulse generator electrically connected to each of the at least 3 electrodes, configured to generate at least one electric field and to deliver the at least one electric field between at least 2 pairs of the at least 3 electrodes to at least one tissue volume underneath the tissue surface, wherein the electric field is generated with parameter values suitable to contract at least one muscle in the tissue volume; a control circuitry, wherein the control circuitry is configured to signal the at least one pulse generator to generate and deliver the at least one electric field in synchronization between the at least 2 pairs or electrodes; at least one battery electrically connected to the control circuitry; a communication circuitry; a control console, comprising: a memory circuitry storing at least one stimulation protocol or indications thereof; a communication circuitry configured to communicate with the at least one stimulation module; 17 a control circuitry, wherein the control circuitry signals the at least one stimulation module to generate and deliver the at least one electric field, according to the at least one stimulation protocol or indications thereof stored in the memory. Example 43. A system according to example 42, wherein the at least one stimulation module comprises at least two stimulation modules, in communication with the control console, and wherein the control console synchronizes activation of the at least two stimulation modules according to the at least one stimulation protocol, to deliver electric fields to at least 2 spacedapart tissue volumes, wherein parameter values of the electric fields are suitable to contract at least 2 muscles, each in a different tissue volume of the at least 2 spaced-apart tissue volumes . Example 44. A system according to any one of examples 42 or 43, wherein the control circuitry of the control console signals the at least one stimulation module to deliver the at least one electric field, during a time period between 10 minutes and 40 minutes while the at least one stimulation module remains coupled to the tissue surface. Example 45. A system according to any one of examples 42 to 44, wherein the control console comprises a user interface configured to generate a human detectable indication with information about an activation status of the at least one stimulation module. Example 46. A system according to example 45, wherein the control console user interface generates the human detectable indication with information about an electrical power level in the at least one battery of the at least one stimulation module. Example 47. A system according to any one of examples 45 or 46, wherein the control console user interface is configured to receive at least one input signal with information about at least one of, electric field intensity, electric field frequency and timing values for delivery of an electric field by the at least one stimulation module, and wherein the control console is used for programming of the at least one stimulation module based on the at least one input signal. Example 48. A system according to any one of examples 42 to 47, wherein the at least one stimulation module comprise at least one position detector configured to detect a position of a stimulation module or a position of each of the at least 3 electrodes of the stimulation module. Example 49. A system according to any one of examples 42 to 48, comprising at least one detector for detecting signals indicating muscle fatigue, and wherein the control console is configured modify activation of the at least one stimulation module based on the detected signals. Example 50. A system according to any one of examples 42 to 49, wherein the at least one pulse generator generates the at least one electric field with a frequency between 25 Hz and 100 Hz, with intensity between 10 mA and 80 mA. 18 Example 51. A system according to any one of examples 42 to 50, wherein the at least one pulse generator repeatedly generates the at least one electric field for a time period between 2 seconds and 12 second with intervals between 1 second and 10 seconds. Example 52. A system according to any one of examples 42 to 51, wherein the at least one stimulation module comprises electrical charging conductors, electrically coupled to the at least one battery, wherein the electrical charging conductors are configured to electrically couple the at least one battery to an external power source. Example 53. An electrode unit, comprising: a housing having a tissue contacting surface configured to be placed in contact directly or indirectly with a tissue surface; at least one electrode within the housing, wherein the electrode comprises an electric connector for connecting the electrode to an external power source; at least one magnetic connector configured to reversibly magnetically couple the at least one electrode to at least one electrical conductor of at least one electrode pad. Example 54. An electrode unit according to example 53, wherein the at least one magnetic connector comprises at least one magnet configured to apply a magnetic field on at least a portion of the at least one electrical conductor. Example 55. An electrode unit according to any one of examples 53 or 54, wherein the at least one magnetic connector comprises at least two spaced apart magnetic connectors configured to reversibly couple the at least one electrode to the at least one electrical conductor of the at least one electrode pad. Example 56. An electrode pad, comprising: a body having a first surface and a second tissue contacting surface coated with an adhesive coating configured to attach the tissue contacting surface to a surface of a tissue: at least two spaced apart electrical conductors crossing through the body between the second tissue contacting surface and the first surface, and extend through the first surface; wherein the at least two spaced apart electrical conductors are configured to conduct electricity through the electrode pad body to a tissue contacting the tissue contacting surface or the adhesive coating. Example 57. A charging module, comprising: a body comprising: a plurality of charging slots shaped as pockets arranged side by side in the body, wherein each charging slot is shaped and sized to receive electrodes of a stimulation module via an opening of 19 the charging slot while keeping a control unit comprising a user interface and charging connectors of the stimulation module outside the charging slot; a plurality of pairs of charging connectors, wherein each pair of the charging connectors is positioned in the body above each opening, and is aligned with the opening; a base configured to allow placing of the charging module on a surface. Example 58. A charging module according to example 57, comprising a plurality of magnetic connectors, each is adjacent to a pair of the charging connectors, wherein each of the plurality of magnetic connectors is configured to magnetically couple the control unit to the body while electrically coupling the control unit charging connectors to the pair of the charging connectors. Example 59. A charging module according to example 57, wherein each pair of the charging connectors of the charging module comprises at least one magnetic connector configured to magnetically couple the control unit to the body while electrically coupling the control unit charging connectors to the pair of the charging connectors. Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. As will be appreciated by one skilled in the art, some embodiments of the present invention may be embodied as a system, method or computer program product. Accordingly, some embodiments of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, some embodiments of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. Implementation of the method and / or system of some embodiments of the invention can involve performing and / or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of some embodiments of the method and / or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware and / or by a combination thereof, e.g., using an operating system. For example, hardware for performing selected tasks according to some embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to some embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to some exemplary embodiments of method and / or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a non-volatile storage, for example, a magnetic hard-disk and / or removable media, for storing instructions and / or data. Optionally, a network connection is provided as well. A display and / or a user input device such as a keyboard or mouse are optionally provided as well. Any combination of one or more computer readable medium(s) may be utilized for some embodiments of the invention. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. 21 Program code embodied on a computer readable medium and / or data used thereby may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for some embodiments of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). Some embodiments of the present invention may be described below with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks. The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other 22 programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. Some of the methods described herein are generally designed only for use by a computer, and may not be feasible or practical for performing purely manually, by a human expert. A human expert who wanted to manually perform similar tasks, such as deliver an electric field between different electrode pairs in synchronization and according to a specific sequence, might be expected to use completely different methods, e.g., making use of expert knowledge and / or the pattern recognition capabilities of the human brain, which would be vastly more efficient than manually going through the steps of the methods described herein. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings and images. With specific reference now to the drawings and images in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings and images makes apparent to those skilled in the art how embodiments of the invention may be practiced. In the drawings: Fig. 1A is a flow chart of a general process for emulating a plyometric exercise by delivery of an electric field to body tissue, according to some exemplary embodiments of the invention; Fig. IB is a flow chart of a general process for delivery of an electric field for contracting simultaneously at least two muscles, for example at least two muscles of a similar muscle group, according to some exemplary embodiments of the invention; Fig. IC shows graphs which demonstrate contraction of two muscles by an alternating electric field, according to some exemplary embodiments of the invention; Figs. 2A-2L show combination of electrode pairs having a shared electrode for generating contraction of muscles at different directions, optionally simultanously, according to some exemplary embodiments of the invention; Figs. 2M-2O show combination of electrode pairs for generating contraction of muscles at different directions (FIG. 2M) and at similar directions (FIGs. 2N and 20), according to some exemplary embodiments of the invention; 23 Fig. 2P is a flow chart of a general process for delivery of an electric field to a subject body in synchronization between upper body and lower body electrodes, for example to emulate a full body muscles exercise, according to some exemplary embodiments of the invention; Fig. 3A is a block diagram of a system for delivery of electrical muscle stimulation (EMS) exercises, according to some exemplary embodiments of the invention; Fig. 3B is a block diagram of a stimulation module of the system shown in fig. 3A, according to some exemplary embodiments of the invention; FIG. 3C is a schematic illustration of a stimulation system, according to some exemplary embodiments of the invention; Fig. 3D is a schematic illustration showing delivery of electric fields between at least 3 electrode pairs which include at least 3 electrodes, according to some exemplary embodiments of the invention; Fig. 3E is a schematic illustration of a signal of an electric field, according to some exemplary embodiments of the invention; Fig. 4 is a flow chart of a process for operating an EMS system, according to some exemplary embodiments of the invention; Fig. 5 is a flow chart of a process performed by an EMS system, according to some exemplary embodiments of the invention; Figs. 6A-6D are schematic illustrations of a stimulation module coupled to electrode patches, according to some exemplary embodiments of the invention; Figs. 7A-7D are schematic illustrations of an electrode pad, according to some exemplary embodiments of the invention; Figs. 8A and 8B are schematic illustrations showing magnetic coupling between electrodes of a stimulation module and electrode patches, according to some exemplary embodiments of the invention; Figs. 9A and 9B are schematic illustrations showing delivery of at least one electric field through a tissue volume, according to some exemplary embodiments of the invention; Figs. 10A and 10B are schematic illustrations of a charging module for wireless stimulation modules, according to some exemplary embodiments of the invention; Fig. 10C is a schematic illustrations of a graphical user interface of an EMS system, according to some exemplary embodiments of the invention; Fig. 10D is an image showing positioning of stimulation modules on a human subject body, according to some exemplary embodiments of the invention; 24 Fig. 10E is an image showing a setup of a stimulation system, according to some exemplary embodiments of the invention; Fig. 10F is an image showing placement of electrode units on a subject body, according to some exemplary embodiments of the invention; Figs. 11A-11G are schematic illustrations and tables (figs. HE and 11G), describing different stimulation protocols, according to some exemplary embodiments of the invention; Figs. 12A-12I are schematic illustrations showing body locations for positioning electrodes, for example electrodes of one or more stimulation modules for delivery of EMS, according to some exemplary embodiments of the invention; Figs. 13A-13E are schematic illustrations showing positioning of electrodes and exemplary electrical stimulation sequences for emulating a standing medicine ball chest pass exercise using EMS, according to some exemplary embodiments of the invention; Fig. 14 is a schematic illustration showing positioning of electrodes and exemplary electrical stimulation sequences for emulating a step up single leg balance with bicep curl exercise using EMS, according to some exemplary embodiments of the invention; and Fig. 15 is a schematic illustration showing positioning of electrodes on a face of a subject, optionally as part of a mask, for delivery of facial EMS, according to some exemplary embodiments of the invention. DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION The present invention, in some embodiments thereof, relates to stimulation of muscles and, more particularly, but not exclusively, to electrical stimulation of muscles. An aspect of some embodiments relates to delivering of an electric field to a body tissue for emulating a plyometric exercise. In some embodiments, the electric field is delivered to body tissue, for example muscles, with parameter values that induce repetitive sessions of rapid extension and contraction of the muscles. In some embodiments, each burst of an electric field is delivered to the muscles for contracting a different group of muscles every up to 4 seconds, for example every 0.5 seconds, every 1 second, every 2 seconds, every 3 seconds, every 4 seconds, or any intermediate, shorter or longer time period. According to some embodiments, the electric field is delivered to at least one muscles group that is activated, for example contracted and released, in at least one plyometric exercise. In some embodiments, the electric field is delivered intermittently to different muscles of a same muscle group, where the muscles are aligned in different directions. In some embodiments, the electric field is delivered intermittently to the muscles of same muscle group with parameter 25 values that are suitable for generating simultaneous contraction periods of the muscle group at different directions. According to some embodiments, an electric field is delivered in synchronization, for example in a pre-determined sequence or simultaneously, to at least one first muscles group and at least one second muscles group, both located in an upper part of the human body above the waist line or in a lower part of the human body below the waist line, and optionally at a same side of the body midline which divides the body into a left side and a right side. Alternatively, the electric field is delivered in synchronization, for example in a pre-determined sequence or simultaneously, to at least one first muscles group located in an upper part of the human body above the waist line and to at least one second muscle group located in a lower part of the human body below the waist line. Optionally, the at least one first and the at least one second muscle groups are located at a same side of the body midline or at opposite sides. According to some embodiments, the first and second muscle groups are muscle groups that participate in a plyometric exercise. In some embodiments, the electric field is delivered in synchronization to the at least one first and the at least one second muscle groups with timing parameters selected to emulate contraction and / or relaxation of muscles of the muscles group during a plyometric exercise. According to some embodiments, the electric field is delivered with parameter values that induce contraction of each muscle during a time period between 0.1 second and 7 seconds, for example between 0.1 second and 3 seconds, between 1 second and 3 seconds, between 1.5 seconds and 3 seconds, between 1.5 seconds and 2.5 seconds, between 2.5 seconds and 5 seconds, between 3 seconds and 10 seconds, or any intermediate, shorter or longer time period. In some embodiments, following electric field delivery, the electric field delivery is stopped, for example to induce muscle contraction, for a time period between 0.1 second and 7 seconds, for example between 0.1 second and 3 seconds, between 1 second and 3 seconds, between 1.5 seconds and 3 seconds, between 1.5 seconds and 2.5 seconds, between 2.5 seconds and 5 seconds, between 3 seconds and 10 seconds, or any intermediate, shorter or longer time period. An aspect of some embodiments relates to contraction in parallel of at least two muscles of a same muscle group, oriented at different directions, by delivery of an electric field. In some embodiments, the electric field is delivered between at least two electrodes with parameter values suitable for contracting a second muscle, while a first muscle remains contracted. In some embodiments, the electric field is delivered alternately between at least two pairs of electrodes, each is positioned to contract a different muscle of the at least two muscles. Optionally, the two electrode pairs have a shared electrode. In some embodiments, the electric field is delivered 26 alternately between three or more pairs of electrodes. Optionally, at least one electrode is shared between the three or more pairs of electrodes. In some embodiments, the electric field is delivered in a frequency of between 80Hz and 120hz, between each pair of electrodes, for example in a frequency between 90Hz and 110Hz, or any intermediate, smaller or larger frequency value. According to some embodiments, the electric field is controllably delivered in synchronization between the at least two pairs of electrodes, for example to induce simultaneous contraction of the at least two muscles oriented at different directions relative to each other. In some embodiments, the electric field is delivered intermittently, for example with stops, to induce continuous repetitive contraction and relaxation of the at least two muscles during a time period of at least 2 seconds, for example a time period of at least 4 seconds, a time period of at least 10 seconds, a time period of at least 30 seconds, a time period of a least 10 minutes, a time period of at least 20 minutes, a time period of at least 30 minutes, or any intermediate, shorter or longer time period, while electrode patches attached to the subject body remain stationary. An aspect of some embodiments relates to delivery of a full body muscle exercise, which involves at least one upper body muscle and at least one lower body muscle, using electric field delivery. In some embodiments, the electric field is delivered in synchronization to upper body electrodes and lower body electrodes to induce synchronous contraction of the at least one upper body muscle and the at least one lower body muscle, for example contraction according to a predetermined sequence or simultaneous contraction. In some embodiments, the at least one upper body muscle and the at least one lower body muscle are positioned at a same side of a body midline. An aspect of some embodiments relates to coupling at least one electrode to at least one electrode patch via magnetic coupling. In some embodiments, the at least one electrode is magnetically removably coupled to the at least one electrode patch attached to a tissue surface, for example a skin surface, to form an electrical conductive path between the electrode and the tissue. In some embodiments, the electrode patch is attached to a flexible skin surface, for example a skin surface above flexible non-rigid tissue such as muscle or fat. According to some embodiment, the electrode is coupled to the electrode patch by at least two separate magnetic portions, for example to prevent relative rotation between the electrode and the electrode patch. Alternatively, the at least one electrode is magnetically coupled, optionally magnetically removably coupled, to the electrode patch via at least one non-circular magnetic connection portion, for example a polygonal magnetic connection portion, which prevents relative rotation between the electrode and the electrode patch. 27 According to some exemplary embodiments, the methods described herein are used for providing physical training and / or cosmetic non-therapeutic treatment to a healthy subject. According to some exemplary embodiments, an electric field delivered between at least one pair of electrodes, as described herein, has an intensity between 1 milliamper (mA) and 80 mA, for example an intensity between 10 mA and 50 mA, an intensity between 20 mA and 40 mA, an intensity between 30 mA and 60 mA, an intensity between 50 mA and 80 mA, or any intermediate, smaller or larger intensity value. According to some exemplary embodiments, an electric field delivered by at least one pair of electrodes, as described herein, has an frequency between 25 Hertz (Hz) and 100 Hz, for example between 25 Hz and 50 Hz, a frequency between 30 Hz and 70 Hz, a frequency between 40 Hz and 80 Hz, or any intermediate, smaller or larger frequency value. According to some exemplary embodiments, an electric field delivered by at least one pair of electrodes, as described herein, has a pulse width between 150 microseconds (ps) and 1150 ps, for example between 150 ps and 300 ps, between 200 ps and 300 ps, between 250 ps and 500 ps, or any intermediate, smaller or larger value, for example about 250ps. An aspect of some embodiments relates to delivery of EMS to facial muscles. In some embodiments, the EMS comprises delivery of electric fields intermittently between two electrode pairs having a shared electrode, where the electrodes are positioned over a face of a subject. In some embodiments, at least one electric field is delivered between two electrodes positioned each on a different side of the face. In some embodiments, the electrodes are part of an EMS mask, optionally integrated in an EMS mask, configured to be placed on a face of subject. According to some embodiments, an electric field is delivered between at least two electrodes positioned over a forehead of a subject, optionally each on a different side of the face. In some embodiments, an electric field is delivered between at least two electrodes positioned at a chin region of the face, each on a different side of the face. Potential advantages of the delivery of electric field by the methods and / or the system and / or the components of a system, for example a stimulation module, as described herein, may include at least one of, delivery of toning and strengthening simultaneously across diverse muscle groups in one treatment session, stimulate multiple muscle groups and body areas simultaneously, controlled muscle stimulation all within a concise 30-minute treatment with no electrode rearrangement, no delays in treatment time which allows greater patient turnover and expedited ROI. Additional potential advantages may include, wireless connectivity untangles and uncomplicates clinicians’ ability to provide a superior treatment across multiple muscle groups 28 without the need for gels, liquids, or belts, different treatment protocols to engage diverse muscle groups without the need to manually rearrange electrodes, thus avoiding treatment interruption. Additional potential advantages may include redefining of toning with up to 16 synchronized electrodes designed to achieve effective stimulation of large muscle groups for muscle strengthening and toning for patients quickly. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. Exemplary electric field delivery for plyometric exercise Without being bound by any particular theory, plyometrics, also known as jump training or plyos, are exercises in which muscles exert maximum force in short intervals of time, with the goal of increasing power (speed-strength). This training focuses on learning to move from a muscle extension to a contraction in a rapid or "explosive" manner, such as in specialized repeated jumping. Plyometrics may include explosive exercises to activate the quick response and elastic properties of the major muscles, and optionally activation of different muscle groups at the same time. According to some exemplary embodiments, electric field is delivered to the subject body at specific, locations, according to at least one specific protocol and / or with parameter values configured to emulate plyometric exercises. In some embodiments, the electric field is delivered in short repetitive bursts that repetitively move at least one muscle or a group of muscles between contraction and extension or between contraction and relaxation. According to some exemplary embodiments, an electric field is delivered to a body of a subject with parameter values and at locations that are suitable for repetitive contraction of at least two spaced-apart muscle groups. In some embodiments, the at least two muscle groups are contracted according to a specific pre-determined sequence or simultaneously. In some embodiments, the at least two muscle groups are muscle groups of the upper body, or at least two muscle groups of the lower body. Alternatively, the at least two muscle groups include at least one muscle group of the upper body and at least one muscle group of the lower body. Reference is now made to fig. 1A depicting delivery of an EMS plyometric exercise to a subject, according to some exemplary embodiments of the invention. According to some exemplary embodiments, at least one exercise region is selected at block 102. In some embodiments, the at least one exercise region is a function and / or an anatomical region in a subject body that participates in at least one plyometric exercise. In some embodiments, the at least one plyometric exercise comprises at least one of, squat jump, tuck jump, tuck squat jump, lateral jump, power skipping, alternate leg bounding, box jumps, vertical depth jump, plyometric push up, broad jump (long jump), pike jump, straddle jump and / or lung jump. According to some exemplary embodiments, the at least one exercise region comprises one or more muscles or muscle groups. Alternatively or additionally, at least one plyometric exercise is selected at block 102. According to some exemplary embodiments, electrodes are positioned on a subject body, at block 104. In some embodiments, the electrodes, for example at least two electrodes, are positioned at specific locations according to the at least one selected exercise region. Alternatively, the at least two electrodes are positioned at specific locations according to a specific plyometric exercise, optionally a plyometric exercise to be emulated by delivery of an electric field, for example by an EMS system. In some embodiments, positioning of the electrodes comprises attaching the electrodes to a skin surface at the at least one selected exercise region. According to some exemplary embodiments, an electric field is delivered to the subject body at block 106. In some embodiments, the electric field is delivered with parameter values and / or according to a protocol suitable for plyometric exercise of the at least one exercise region. Alternatively or additionally, the electric field is delivered with parameter values and / or according to a protocol suitable for emulating at least one selected plyometric exercise optionally selected at block 102. According to some exemplary embodiments, the electric field is delivered with parameter values suitable for inducing repetitive rapid contraction and expansion or relaxation of at least one muscle group. In some embodiments, the delivered electric field induces simultaneous repetitive contraction of muscles substantially aligned in a similar direction and / or simultaneous contraction of muscles substantially oriented at angle relative to each other. According to some exemplary embodiments, the different electric fields induce repetitive contraction of at least two muscle groups located at a distance larger than 3 cm from each, for example at a distance larger than 5 cm, larger than 10 cm, larger than 20 cm, larger than 25 cm, larger than 30 cm, larger than 35 cm, or any intermediate, smaller or larger distance from each other. In some embodiments, the different electric fields are delivered intermittently or 30 sequentially to contract the at least two muscle groups simultaneously or according to a predetermined sequence. Exemplary simultaneous contraction of at least two muscles According to some exemplary embodiments, at least two muscles are contracted during a treatment, for example an EMS treatment. In some embodiments, the at least two muscles are contracted at different directions, oriented at an angle larger than 10 degrees, for example larger than 20 degrees, larger than 30 degrees, larger than 40 degrees, larger than 50 degrees, larger than 60 degrees, or any intermediate, smaller or larger value relative to each other. In some embodiments, the at least two muscles are contracted at different directions, oriented at an angle between 10 degrees and 120 degrees therebetween, for example at angle between 30 degrees and 100 degrees, at an angle between 30 degrees and 60 degrees, at an angle between 45 degrees and 100 degrees, or any intermediate, smaller or larger angle therebetween. According to some exemplary embodiments, simultaneous contraction of different muscles of a single muscles group allows for example, an efficient muscles training by training more muscles in a shorter time period. In some embodiments, simultaneous contraction of different muscles of a region, allows for example, an exercise regime that covers large muscles groups, for example per region, in a shorter time period. Reference is now made to fig. IB, depicting a process for simultaneous contraction of at least two muscles using synchronized electric fields, according to some exemplary embodiments of the invention. According to some exemplary embodiments, at least 3 electrodes are placed in contact with tissue, at block 110. In some embodiments, the at least 3 electrodes are placed in contact with a skin surface, optionally above at least two target muscles. In some embodiments, the at least 3 electrodes comprise 3 electrodes ,4 electrodes ,5 electrodes ,6 electrodes ,7 electrodes, or any smaller or larger number of electrodes. In some embodiments, the at least 3 electrodes are electrically connected to at least one pulse generator. In some embodiments, the pulse generator is configured to generate electric fields and to deliver the electric fields via different pairs of the at least 3 electrodes, optionally in synchronization between the different electrode pairs. According to some exemplary embodiments, a first electric field, for example a first electric pulse, is delivered with parameter values suitable to contract a first target muscle, at block 112. In some embodiments, the first electric field is delivered between a first pair of electrodes of the at least 3 electrodes. In some embodiments, the electric field contracts the first 31 target muscle for a prolonged contraction time period which exceeds the electric field delivery time via the first pair of electrodes. According to some exemplary embodiments, a second electric field, for example a second electric pulse, is delivered with parameter values suitable to contract a second target muscle, at block 114. In some embodiments, the second electric field is delivered between a second pair of electrodes of the at least 3 electrodes, optionally using a shared electrode between the first electrodes pair and the second electrodes pair. In some embodiments, the second electric field is delivered during the prolonged contraction time period of the first target muscle, resulting with simultaneous contraction of the two target muscles. In some embodiments, the two electric fields, for example two electric field pulses, are delivered in synchronization between the two different electrode pairs, such that the two muscles remain simultaneously contracted during at least 50% of the delivery time of the electric fields, for example during at least 60%, during at least 70%, during at least 80%, during at least 90%, during at least 95% or any intermediate, smaller or larger percentage value of the electric fields delivery time. Reference is now made to fig. IC, depicting synchronization of electric field pulses for simultaneous contraction of at least two muscles, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a first electric field is delivered, for example as a biphasic pulse 130 between T1 and TO, with parameter values suitable to contract a first muscle 132. In some embodiments, the pulse 130 is delivered between a first pair of electrodes, optionally positioned on a skin surface above the muscle 132. In some embodiments, the pulse is stopped at Tl. According to some exemplary embodiments, a second electric field is delivered, for example as a biphasic pulse 134, when pulse 130 is stopped. In some embodiments, the pulse 134 is delivered via a second pair of electrodes to the muscle 136. Optionally, the second pair of electrodes is positioned on a skin surface above muscle 136. In some embodiments, the pulse 134 is delivered with parameter values which are suitable for contraction of the muscle 136. In some embodiments, the pulse 134 is delivered to muscle 136 while muscle 132 remains contracted. According to some exemplary embodiments, the first and second pulses 130 and 134 are delivered intermittently and in synchronization, optionally during a contraction period of the muscles 136 and 132 respectively for simultaneous contraction of the muscles 132 and 136 during a time period between T4 and Tn, as shown in fig. IC. Reference is now made to figs. 2A-2M depicting different configurations for electric field conduction paths between at least 4 electrodes, for example 4 electrodes of a single stimulation 32 module, according to some exemplary embodiments of the invention. In some embodiments, at least one electric field is intermittently delivered by two pairs of electrodes, optionally having a shared electrode, at two different paths. However it should be understood that electric field can be intermittently delivered between a larger number of electrode pairs of the at least 4 electrodes. In some embodiments, at least one muscle in each electric field conduction path is contracted in response to the delivered electric field. According to some exemplary embodiments, each of the figs. 2A-2M shows a configuration of a plurality of electric field conduction paths between each pair of electrodes of the 4 electrodes shown, for example paths 202, 204, 206 and 208In some embodiments, in order to generate contraction of one or more muscles, at least 3 electrodes, for example electrodes 1, 2, 3, 4 are positioned on a skin surface above the muscles, optionally in a quadrilateral configuration. In some embodiments, the at least 3 electrodes are electrically coupled to at least one pulse generator. In some embodiments, for example as shown in figs. 2A-2L, delivering electric fields via different pairs of electrodes in the paths within the tissue marked by the arrows, for example as also described in fig. IC, induces contraction of muscles located in these paths that are affected by the delivered electric field. Optionally, the electric fields are delivered using two electrode pairs having a shared electrode, marked in the figures with a circle. According to some exemplary embodiments, the intermittent delivery of the at least one electric field in two separate paths induces alternating or simultaneous contraction of muscles at this paths. In some embodiments, for example as shown in figs. 2A-2D the electric field paths have a L-shaped pattern. In some embodiments, for example as shown in figs. 2E-2L, the electric field paths have a V-shaped pattern. Optionally, for example as shown in fig. 2M, the electric field paths cross each other, forming an X configuration. Optionally, for example as shown in figs. 2N and 20, the electric field paths are optionally oriented at the same general direction. In some embodiments, for example as shown in figs. 2M-2O, there is no shared electrode between the electrode pairs generating the 2 electric field paths. Exemplary full body training According to some exemplary embodiments, a system for EMS treatment, also termed herein as training or exercise, is used to provide a full body training, by optionally inducing synchronized contraction of two or more muscle groups located in the same side of the body, and of contralateral corresponding muscle groups. Additionally or optionally, the system provides a 33 full body workout by inducing synchronized contraction of two or more muscle groups located at different parts of the body, for example at least one muscle group located at the upper body above the waist line, and at least one muscle group located at the lower body below the waist line. According to some exemplary embodiments, synchronized contraction of muscles comprises simultaneous contraction, sequential contraction or overlapping contraction when at least some of the treatment time the two muscle groups are contracted simultaneously. Reference is now made to fig. 2P, depicting a process for a full body training, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a stimulation system, for example an EMS system, receives at least one input signal about a selected full body stimulation treatment, at block 220. In some embodiments, the input signal is received from a user interface associated with the system, for example a user interface of a control unit or a console, or a user interface of an application software which is in communication with the system. According to some exemplary embodiments, the input signal comprises information about at least one specific exercise or about two or more muscle groups to be included in the training. According to some exemplary embodiments, an indication to position electrode patches is delivered at block 222. In some embodiments, the indication includes information about target location of the electrodes on the body, for example on a skin surface. In some embodiments, the indication is an audio and / or a visual indication. Optionally the indication is color coded, such that each electrode patch is shown in a different color. Optionally, the indication is delivered with at least one user interface of the system. Optionally, the indication comprises a map showing a subject body, for example a general body scheme or a scheme of the specific subject, with target locations for positioning of the electrode patches. According to some exemplary embodiments, a full body stimulation treatment is initiated, at block 224. In some embodiments, a human detectable indication, for example, an audio and / or a visual indication, is delivered when the treatment initiates, optionally by a user interface of the system. According to some exemplary embodiments, during the treatment, at least one electric field or a plurality optionally different, electric fields, is delivered in synchronization between electrodes coupled to the electrode patches. In some embodiments, the at least one electric field or the plurality of electric fields is delivered in synchronization between different electrode pairs, each is located above a different muscle or above different muscle groups, at spaced-apart body regions, for example, above an abdomen, above a chest, above shoulders, above the back, above a buttock, and / or above one or more leg parts. Exemplary system Reference is now made to fig. 3A, depicting a system for delivery of EMS treatments, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a system 302 is configured to deliver one or more treatments to a subject body. In some embodiments, the one or more treatments comprise aesthetic treatments, for example to improve skin laxity, lift and / or tone. In some embodiments, the one or more treatment comprises treatments for muscle firming and toning. Optionally, the one or more treatments comprise ultrasound treatments. In some embodiments, the system is configured to provide an ultrasound treatment and a muscle stimulation treatment to different regions of the body or to the same region of the body. Optionally, both muscle stimulation treatment and ultrasound treatment are delivered by the system, each to a different region or both to the same region of a subject body, sequentially or in parallel, during a same treatment session. A potential advantage of providing both an ultrasound treatment and an electrical muscle stimulation treatment to different or same body parts during the same treatment session may be a decreased overall treatment duration, consequently resulting in cost savings related to personnel labor and infrastructure utilization. In some embodiments, the ultrasound treatment is delivered, for example as described in at least one of International Patent Applications Publication Numbers WO2017212489A2, WO2020194312A1, WO2023089625A1, and WO2020026253A2, incorporated herein as a reference in their entireties. According to some exemplary embodiments, the system 302 is used for stimulating different muscle groups in synchronization, via at least 6 electrodes, for example at least 8 electrodes, via at least 12 electrodes, via at least 16 electrodes, or any smaller or larger number of electrodes for both sides of the body, optionally without changing position of the electrodes during a treatment session. In some embodiments, each treatment session lasts between 10 minutes and 60 minutes, for example between 10 minutes and 30 minutes, between 20 minutes and 40 minutes, between 25 minutes and 35 minutes, between 20 minutes and 60 minutes, or any intermediate, shorter or longer duration. Optionally, during a treatment session, the subject is at a resting position optionally contacting a support structure. According to some exemplary embodiments, the system 302 comprises a control console 304, and at least one stimulation module, for example stimulation modules 306 and 308, in communication, for example wireless communication with the console 304. In some embodiments, the stimulation modules 306 ad 308 are configured to be coupled, optionally removably coupled, to a tissue, for example to a skin surface of a subject and to remain coupled to the tissue during at least one treatment session. In some embodiments, the stimulation modules 35 are configured to be coupled, optionally removably coupled to at least one electrode patch adhered to the subject tissue, for example to the skin surface. In some embodiments, the system 302 comprises a charging module 310, for charging the at least one stimulation module. According to some exemplary embodiments, the stimulation module, for example each of the modules 306 and 308, comprises a control unit 312 and at least two electrode units, for example electrode units 314. In some embodiments, the electrode units 314 are electrically connected to the control unit 312, via at least one electric wire. According to some exemplary embodiments, each of the electrode units 314 comprises at least one electrode 316 configured to deliver an electric field to a tissue, optionally transcutaneously, received from a pulse generator in the control unit 312. In some embodiments, each or at least some of the electrode units 314 of a stimulation module 306 comprise at least one detector 318, for example an electrode or a sensor. In some embodiments, the at least one detector 318 comprises a position sensor and / or an accelerometer. In some embodiments, the at least one detector 318 is configured to detect a position and / or orientation of an electrode unit 314. Alternatively or additionally, the at least one detector 318 comprises a sensor for measuring at least one physiological parameter indicating muscle contraction. According to some exemplary embodiments, the at least one detector is configured to detect signals indicating muscle fatigue. In some embodiments, the control circuitry 324 of the stimulation module is configured to control activation of the pulse generator according to the signals received from the at least one detector. For example, in some embodiments, the control circuitry 324 is configured to stop generation of an electric field by the pulse generator 322 if muscle fatigue is detected, based on signals received from the at least one detector 318. Alternatively, the control circuitry 324 modifies at least one parameter of the electric field and / or timing for delivery of the electric field based on signals received from the at least one detector 318, optionally indicating muscle fatigue. According to some exemplary embodiments, the system 302 is configured to receive signals from at least one external detector, which indicate muscle fatigue, and to optionally modify activation of one or more stimulation modules according to the received signals. In some embodiments, the at least one detector 318 or the external detector comprises an Electromyography (EMG) detector. According to some exemplary embodiments, each of the electrode units 314 comprises a user interface (UI) 320. In some embodiments, the UI 320 is configured to generate a human detectable indication, for example an audio and / or a visual indication. In some embodiments, the UI 320 generates a human detectable indication with information about a position of the electrode 36 unit, for example to indicate that the electrode unit 314 is at a target location on a subject body. Alternatively or additionally, the UI 320 generates a human detectable indication with information about current activity of the electrode unit 314. According to some exemplary embodiments, a control unit 312 of each stimulation module 306 and 308 comprises at least one electrode 316, configured to deliver an electric field to tissue optionally transcutaneously. In some embodiments, each control unit 312 comprises a pulse generator 322, electrically coupled to the electrode 316 of the control unit 312 and to the electrodes 316 of the electrode units 314.In some embodiments, the pulse generator 322 is configured to generate an electric field and to deliver the electric field to at least one pair of the electrodes 318. According to some exemplary embodiments, a control unit 312 comprises a control circuitry 324 and a power source 326. In some embodiments, the power source 326 comprises at least one battery, for example a rechargeable and / or a replaceable battery. In some embodiments, the power source 326 is electrically connected to one or more charging connectors 328, configured to allow electrical charging of the power source 326 from an external power source. According to some exemplary embodiments, a control unit 312 comprises at least one detector 318, for example an electrode or a sensor. In some embodiments, the at least one detector 318 comprises a position sensor and / or an accelerometer. In some embodiments, the at least one detector 318 is configured to detect a position and / or orientation of the control unit 312. Alternatively or additionally, the at least one detector 318 comprises a sensor for measuring at least one physiological parameter indicating muscle contraction. According to some exemplary embodiments, a control unit 312 comprises a user interface (UI) 320. In some embodiments, the UI 320 is configured to generate a human detectable indication, for example an audio and / or a visual indication. In some embodiments, the UI 320 generates a human detectable indication with information about a position of the control unit 312, for example to indicate that the control unit 312 is at a target location on a subject body. Alternatively or additionally, the UI 320 generates a human detectable indication with information about current activity of the control unit 312 and / or about current activity of the stimulation module, for example module 306 or module 308. According to some exemplary embodiments, a control unit 312 comprises a communication circuitry 330. In some embodiments, the communication circuitry 330 of each stimulation module, is configured to transmit and / or receive signals, for example wireless signals from the console 304. Optionally, the communication circuitry 330 of a stimulation module is 37 configured to receive and / or transmit signals from and / or to at least one different stimulation module. According to some exemplary embodiments, each of the stimulation modules 306 and 308, for example each of the control unit 312 and the electrode units 314, are configured to be coupled, optionally removably coupled, to at least one electrode patch, for example to a patch already adhered to a skin surface of the subject. In some embodiments, each of the control unit 312 and each of the electrode units 314 is configured to be coupled, optionally removably coupled to a different electrode patch on the subject skin surface, for example to allow individual separate electrical connection between each electrode 316 of a stimulation module with the skin surface of the subject. According to some exemplary embodiments, a control console 304 comprises a control circuitry 332 and a memory, for example a memory circuitry 333. In some embodiments, the control console 304 comprises a user interface 334. In some embodiments, the user interface 334 is configured to deliver and / or receive information from a user operating the system, for example a therapist or a trainer. In some embodiments, the user interface 334 is configured to deliver a human detectable indication, for example, an audio and / or a visual indication to the user. In some embodiments, the user interface 334 comprises a keyboard and / or a display, for example a touch pad display. According to some exemplary embodiments, the control console 304 comprises a communication circuitry 336. In some embodiments, the communication circuitry 336 is configured to communicate, for example to deliver and / or receive signals from the stimulation modules 306 and 308, optionally via a communication circuitry 330 of each stimulation module. Optionally, the communication circuitry 336 is configured to communicate with the charging unit 310. In some embodiments, the communication circuitry 336 is configured to deliver and / or to receive wireless signals, for example Bluetooth, Bluetooth Low Energy (BLE), Wi-Fi, infrared, and radio signals. According to some exemplary embodiments, the control circuitry 332 of the control console is configured to control the activation of each of the stimulation modules 306 and 308, for example a synchronized activation of the stimulation modules 306 and 308, based on treatment parameter values and / or at least one treatment protocol stored in the memory 333. Alternatively or additionally, the control circuitry 332 controls the activation of the stimulation modules based on input received via the user interface 334 of the console 304. According to some exemplary embodiments, the control circuitry 332 signals the communication circuitry 336 to transmit signals, for example wireless signals to the stimulation 38 modules 306 and 308 with activation parameters of each of the electrodes 316 of a stimulation module. In some embodiments, the signals include synchronization information between the different electrodes of each stimulation module, and / or between different stimulation modules. In some embodiments, the console 304 programs each of the stimulation modules that are attached to a subject body with activation parameter values, and / or synchronization information. In some embodiments, the console 304 programs the stimulation modules before initiating a treatment program and / or during a treatment session while an electric field is delivered to the subject body. According to some exemplary embodiments, the console 304 receives information from each of the stimulation modules, for example modules 306 and 308, about a charging level of each of the power sources 326 of each module, about a position of each module on a subject body, about a state of an electrical conductance path between each electrode and the tissue surface, and / or about an activation state of each module or an activation state of each electrode 316 of a stimulation module. In some embodiments, the console 304 generates a human detectable indication by the user interface 334 to a user of the system based on the information received from the stimulation modules. In some embodiments, the human detectable indication is generated prior to initiation of the stimulation treatment or treatment session, and / or during the treatment session. According to some exemplary embodiments, the console 304 is electrically connected to a power source, for example an external power source 340. Optionally, the console 304 is functionally coupled to at least one ultrasound applicator 342. In these embodiments, the memory 333 comprises parameter values of ultrasound waves to be generated by the ultrasound applicator 342 and / or at least one ultrasound treatment protocol. In some embodiments, the console is configured to deliver one or more ultrasound treatments based on the information stored in the memory 333, using the at least one ultrasound applicator 342. According to some exemplary embodiments, the charging module 310 comprises charging connectors 344 configured to mechanically and / or structurally fit and interact with charging connectors 328 of the stimulation modules 306 and 308. In some embodiments, the charging module 310 comprises a control circuitry 346, a user interface 348 which is optionally similar to user interfaces 320 and 334, and a communication circuitry 350 which is optionally similar to communication circuitry 336. According to some exemplary embodiments, when they are not used for a stimulation treatment, the stimulation modules are coupled to the charging module 350, for example and to the charging connectors 344 for charging the power source 326 of each stimulation module. In some embodiments, the user interface 348 generates a human detectable indication with 39 information about the charging level of each power source 326 connected to the charging connectors 344, or when the power source is fully charged. Alternatively or additionally, the communication circuitry 350 sends a signal for example a wireless signal to the console 304 with the information about the charging of the stimulation modules. Optionally, user interface 334 generates an indication based on the information received from the charging module 310. In some embodiments, the charging module 310 is electrically connected to an external power source 350. Reference is now made to fig. 3B, depicting a stimulation module block diagram, for example a multiplexing stimulation module, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a stimulation module 360 comprises at least 3 electrodes each in a different electrodes unit, for example units 362, 364, 366 and 368. In some embodiments, each electrode unit is configured to be positioned at a distance of between 2 cm and 40 cm, for example between 2 cm and 20 cm, between 5 cm and 20 cm, between 10 cm and 30 cm, or any intermediate, smaller or larger distance from a different electrode unit, on a subject body. According to some exemplary embodiments, each or at least one or some of the electrode units comprise a sensor, which is similar to the detector 318. According to some exemplary embodiments, each of the units 362, 364, 366 and 368 is functionally coupled to a multiplexer 370. In some embodiments, the multiplexer is configured to deliver at least one electric field or different electric fields in synchronization to different electrode pairs of the units. For example, as shown in fig. 3B, the multiplexer is configured to deliver intermittently and in synchronization a first electric field to electrodes 1 and 2 of units 362 and 364 respectively, and a second electric field to electrodes 2 and 3 of units 364 and 366 respectively. According to some exemplary embodiments, electric fields are delivered between at least 3 electrode pairs, for example between electrodes of units 362 and 364, between electrodes of units 364 and 366, and between electrodes of units 362 and 366. Optionally, the electric fields are delivered intermittently between the at least 3 pairs. Optionally, the electric field is delivered with a frequency between 50 Hz and 150Hz between electrodes of each pair, for example with a frequency of about 60 Hz, with a frequency of about 80Hz, with a frequency of about 100 Hz, with a frequency of about 110 Hz, or any intermediate, smaller or larger frequency value. In some embodiments, the electric fields are delivered repetitively while alternating between the two electrode pairs during at least 1 second, for example during at least 2 seconds, during at least 10 40 seconds, during at least 1 minute, during at least 10 minutes, or any intermediate, shorter or larger time period. According to some exemplary embodiments, the multiplexer 370 is functionally coupled to a pulse generator 374 configured to generate the electric field, and to a controller 372. In some embodiments, the multiplexer 370 receives the at least one electric field or the electric fields generated by the pulse generator 374, delivers the at least one electric field or the electric fields to at least two electrode pairs, based on signals received from the controller 372. Optionally, at least one electrode unit, for example at least one electrode is shared between the two electrode pairs, for exmaple as shown in fig. 3B, electrode 2 of unit 364 is shared between the two electrode pairs 1-2 and 2-3. According to some exemplary embodiments, the controller 372 s functionally coupled to a communication circuitry, for example a Bluetooth controller 376. In some embodiments, the Bluetooth controller receives wireless signals from at least one of, a different stimulation module, or a console, with parameter values for generating at least one electric field and with synchronization information. In some embodiments, the pulse generator 374 uses the received parameter values for generating the at least one electric field. Additionally, the controller 372 and / or the multiplexer 370 use the synchronization information for generating a multiplexed signal by alternating in synchronization between the two electrode pairs. According to some exemplary embodiments, at least two stimulation modules, for example stimulation modules 306 and 308, are electrically connected, for example to generate a single stimulation unit comprising at least 6 separate electrodes. In some embodiments, the single stimulation module is configured to generate and deliver an electric field between different electrode pairs of the single stimulation module, optionally using at least one shared electrode. In some embodiments, a stimulation program stored in a memory of a control console or in a memory of a stimulation module defines which electrodes of the stimulation module will be used for stimulation during a specific time period, according to position of the electrodes relative to target muscles intended to be stimulated, according to an exercise to be delivered using the EMS, and / or according to location of tissue not intended to be stimulated, for example nerve tissue. Exemplary stimulation via at least 3 electrodes Reference is now made to fig. 3D, depicting using at least 3 electrode pairs for delivery of stimulation, according to some exemplary embodiments of the invention. According to some exemplary embodiments, at least 3 electrodes, for example electrodes 365, 367 and 369, are placed on a subject body 371. In some embodiments, the electrodes are positioned at a distance between 2 centimeters (cm) and 40 cm therebetween, for example at a distance between 2 cm and 10 cm, at a distance between 5 cm and 20 cm, at a distance between 10 cm and 40 cm therebetween, or any sorter or longer distance therebetween, for example between electrodes used as an electrodes pair for delivery of stimulation to the subject body, optionally to the subject muscles. In some embodiments, the electrodes 365, 357 and 369 are attached to the skin surface above a target stimulation region, for example above a selected stimulation target. In some embodiments, the target stimulation region comprises at least two muscles, at least 3 muscles, at least muscles, or any larger number of muscles, selected to be stimulated. In some embodiments, each of the electrodes 365, 367 and 369 is part of a separate stimulation module and / or part of an electrode unit, for example as described in fig. 3A. According to some exemplary embodiments, electric fields are delivered, optionally in alternation, between electrode pairs 365 and 367, 365 and 369, 367 and 369. In some embodiments, the electric fields are delivered with the same parameter values, according to a stimulation sequence, comprising the order of electric field delivery between electrode pairs. Alternatively, at least one electric field of the electric fields delivered between the 3 electrode pairs is delivered with different parameters. In some embodiments, the electric field parameter values are selected according to the location of the electrode pairs in the subject body, according to tissue composition at the electrodes placement site, according to the depth of muscle layer from the skin surface, and / or according to the presence and / or proximity of tissue that should not be stimulated, for example nerve tissue. According to some exemplary embodiments, electric fields are delivered intermittently between electrodes of at least 3 electrode pairs, for example between electrodes 0 and 1 of a first electrode pair, between electrodes 0 and 2 of a second electrode pair, and between electrodes 0 and 3 of a third electrode pair, having electrode 0 as a shared electrode. In some embodiments, the electric fields are delivered between the electrode pairs intermittently with timing parameters suitable to induce simultaneous contraction, for example during at least 80%, at least 90% at least 95%, or any intermediate smaller or larger percentage value of a single stimulation time window, of at least 3 different muscles. In some embodiments, a pulse generator generates electric field pulses with a frequency value that is divided between the at least 3 electrode pairs. For example, the pulse generator generates electric field pulses in 450 Hz, and when alternating between 3 electrode pairs, each electrode pair receives an electric field pulse with 150Hz. Exemplary pulse signal Reference is now made to fig. 3E, depicting a signal of an electric field, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a signal 380, is a biphasic signal comprises pulses. In some embodiments, a pulse width 386 of a pulse 382, has a duration between 100 ps and 1150 ps, for example between 150 ps and 300 ps, between 200 ps and 500 ps, between 400 ps and 1150 ps, or any intermediate, smaller or larger value. In some embodiments, the stimulation pulse width, for example pulse width 386 is between 30 ps and 700 ps, for example between 50 ps and 200 ps, between 100 ps and 300 ps, between 200 ps and 500 ps, between 400 ps and 700 ps, or any intermediate, smaller or larger value. According to some exemplary embodiments, a pulse width 386 comprises a plus phase 388 and a minus phase 390 each having a duration between 100 ps and 500 ps, for example between 100 ps and 300 ps, between 200 ps and 400 ps, between 300 ps and 500 ps, or any intermediate, smaller or larger value. In some embodiments, the pulse width comprises an intra phase 392 between the plus phase 388 and the minus phase 390. In some embodiments, a duration of the intra phase 392 is between 50 ps and 500 ps, for example between 50 ps and 200 ps, between 100 ps and 300 ps, between 250 ps and 500 ps, or any intermediate, smaller or larger value. In some embodiments, a duration of the intra phase 392 is between 50 ps and 150 ps, for example between 50 ps and 100 ps, between 50 ps and 80 ps, between 70 ps and 120 ps, or any intermediate, smaller or larger value. According to some exemplary embodiments, the signal 380 is symmetric. Alternatively, the signal is asymmetric. According to some exemplary embodiments, an ON time in which an electric field is delivered between at least two electrodes is between 0.5 second and 40 seconds, for example between 1 second and 20 seconds, between 1 second and 10 seconds, between 5 seconds and 20 seconds, between 10 seconds and 25 seconds, between 20 seconds and 40 seconds, or any intermediate, shorter or longer ON time. According to some exemplary embodiments, an OFF time in which electric field delivery is stopped, is between 0.5 second and 40 seconds, for example between 1 second and 20 seconds, between 1 second and 10 seconds, between 5 seconds and 20 seconds, between 10 seconds and 25 seconds, between 20 seconds and 40 seconds, or any intermediate, shorter or longer OFF time. According to some exemplary embodiments, the stimulation, for example the electric field delivered between at least two electrodes is delivered with a frequency of between 1Hz and 200 Hz, for example with a frequency between 1Hz and 150Hz, with a frequency between 1Hz 43 and 20Hz, with a frequency between 10Hz and 50Hz, with a frequency between 30Hz and 60Hz, with a frequency between 50Hz and 100 Hz, with a frequency between 80Hz and 200Hz, or any intermediate, smaller or larger frequency value. According to some exemplary embodiments, stimulation is delivered as part of a muscle training program, for treating or shaping at least one muscle of the arms body region, at least one muscle of the calves body region, at least one muscle of the upper back body region and / or at least one muscle of the lower back body region. Exemplary muscle stimulation process- user activities Reference is now made to fig. 4, depicting a process for muscle stimulation, for example EMS, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a system is switched on, at block 402. In some embodiments, the system comprises system 302 shown in fig. 3A. In some embodiments, a console, for example console 304 is switched on. Additionally, and optionally, the charging module 310 which includes at least one stimulation module, is switched on at block 402. According to some exemplary embodiments, a user selects an EMS application, at block 404. In some embodiments, the user selects the EMS application using the user interface 334. In some embodiments, selecting an EMS application comprises selecting at least one EMS protocol. According to some exemplary embodiments, subject parameters are optionally selected at block 406. In some embodiments, selecting subject parameters comprises inserting input information about the subject, for example at least one of, subject weight, subject height, subject age, subject gender, subject Body Mass Index (BMI), subject body measurements, and / or subject medical history. In some embodiments, inserting or selecting subject parameters is used, for example to personalize at least one parameter of the application or protocol selected at block 404 to a specific subject. According to some exemplary embodiments, treatment areas are optionally selected at block 408. In some embodiments, the treatment areas comprise at least one of, Abdominal muscles, Quadriceps, Gluteus tights, Hamstrings, Biceps, Triceps and Calf muscles . Alternatively, the treatment areas already selected when selecting the EMS application or EMS protocol. In some embodiments, one or more region of interest (ROI) for a treatment comprise, at least one ROI at an abdomen of a subject body, at least one ROI at a leg of the subject body, at least one ROI at a buttocks region of the subject body, at least one ROI at a chest region of the 44 subject body, at least one ROI at a shoulders region of the subject body, and / or at least one ROI at a back region of the subject body. According to some exemplary embodiments, an indication is optionally received form the stimulation modules, at block 410. In some embodiments, the indication, for example a human detectable indication, indicates a charging level of each stimulation module, and whether they can be placed on a subject body and deliver an electric field to the subject body. According to some exemplary embodiments, electrode pads, also termed herein as electrode patches, are placed on the subject body. In some embodiments, the electrode pads are adhered to the subject body, for example to the skin surface via an intermediate layer of adhesive, for example glue. According to some exemplary embodiments, a user of the system adheres the electrode patches to the subject body, based on an indication for example a visual indication showing one or more specific location for placing the electrode pads. Optionally the locations are based on the application selected at block 404 and / or based on the selected treatment areas optionally selected at block 408. Optionally, the electrode pad provides a human detectable indication if the pad is attached to the specific location. According to some exemplary embodiments, stimulation modules of the system are coupled, optionally removably coupled, to the electrode pads, at block 414. Optionally, each electrode of the stimulation module is functionally coupled to a different electrode pad. According to some exemplary embodiments, a human detectable indication, for example a visual indication is received for correct positioning of the stimulation modules, at block 416. In some embodiments, the indication indicates that each electrode is correctly positioned on a subject body. Optionally, each electrode unit, for example units 314 and / or a control unit 312 of a stimulation module delivers the indication. According to some exemplary embodiments, a protocol or protocol parameter values are optionally selected at block 418. Alternatively, a protocol or parameter value are adjusted prior to initiating a treatment. According to some exemplary embodiments, treatment is initiated at block 420. According to some exemplary embodiments, input is optionally received form the system, at block 422. In some embodiments, the input comprises information about at least one of, a progress of the treatment, time from beginning of the treatment, remaining time, battery charging levels of the stimulation modules, activity of each stimulation module and / or electrode, and / or information about the contraction of one or more muscles. 45 According to some exemplary embodiments, input is optionally received from the subject, at block 424. In some embodiments, the input comprises information about pain and / or discomfort. According to some exemplary embodiments, values of one or more parameters of the treatment are optionally adjusted at block 426. In some embodiments, the one or more parameters comprise treatment duration, intensity of at least one electric field, and / or frequency of at least one electric field. In some embodiments, the one or more treatment parameter value is adjusted based on the input optionally received form the system at block 422 and / or based on the input optionally received form the subject at block 424. According to some exemplary embodiments, an indication about an end of the treatment is received at block 428. Exemplary muscle stimulation process- system activities Reference is now made to fig. 5, depicting system activities during a muscle stimulation treatment, for example EMS, according to some exemplary embodiments of the invention. According to some exemplary embodiments, the system receives input about selected treatment area, at block 502. Alternatively or additionally, the system receives input about a selected muscle exercise. In some embodiments, the system receives the input from a user of the system using at least one user interface associated with the system, for example user interface 334 of console 304 shown in fig. 3A. According to some exemplary embodiments, the system provides an indication for target positions on a subject body for placing electrodes, at block 504. In some embodiments, the indication is a color coded indication. In some embodiments, the system provides the indication using the user interface 334, optionally showing the target locations on a map of a human subject body. According to some exemplary embodiments, the system receives input about position of each electrode, at block 506. In some embodiments, the system receives information about a position of each electrode from at least one detector, for example detector 318 which is located in each electrode unit 314 and a control unit 312 of a stimulation module, for example modules 306 and 308 shown in fig. 3A. In some embodiments, the at least one detector comprises an accelerometer, lead zirconium titanate (PZT) or any other position sensor. According to some exemplary embodiments, the system delivers an indication, for example a visual indication about the position of each electrode, at block 508. In some embodiments, the visual indication is a light indication delivered if the electrode is at a target 46 location and / or if the electrode is misplaced. In some embodiments, the visual indication is delivered by the user interface 334 of the console 304, or by a user interface of each unit of a stimulation module, for example user interface 320 of electrodes unit 314 and of the control unit 312. Additionally or optionally, an indication, for example a visual indication, that each electrode of the stimulation module is securely coupled to an electrode pad, is delivered to the user. According to some exemplary embodiments, a muscle stimulation treatment is initiated at block 510. In some embodiments, the muscle stimulation treatment is initiated if all of the electrodes are positioned at target locations, are securely coupled to electrode pads and / or have an electrical conducting path to the subject body. According to some exemplary embodiments, an electric field is delivered in synchronization between electrode pairs of a stimulation module, at block 512. In some embodiments, the electric field is delivered in synchronization between two electrode pairs of a single stimulation module, for example intermittently, optionally using a shared electrode. In some embodiments, the electric field is delivered intermittently with timing parameters suitable for contracting at least two muscles simultaneously. In some embodiments, the at least two muscles are contracted by electrodes of the same stimulation module at different directions. In some embodiments, the two muscles are muscles related to the same muscle group or are positioned at the same anatomical region of the body, for example at a same side of the body midline or in an area smaller than 1600 cm2, for example in an area smaller than 900 cm2, in an area smaller than 400 cm2, or any intermediate, smaller or larger surface area to which the electrodes of the single stimulation module are attached. . Alternatively or additionally, the electric field is delivered in synchronization, for example in a timed synchronization, between at least two different stimulation modules. Optionally, the stimulation modules are located at different body regions in a same side of the body midline. In some embodiments, at least one stimulation module is positioned on an upper body of the subject above the waist line, and at least one second stimulation module is positioned on a lower body of the subject below the waist line, in the same side of the body midline or in opposite sides. In some embodiments, the at least two different modules are activates to generate simultaneous or sequential contraction of muscles below the stimulation modules. According to some exemplary embodiments, the system ends the stimulation treatment at block 516. 47 According to some exemplary embodiments, an indication for safe removal of electrodes and / or of the stimulation modules is optionally delivered at block 518. According to some exemplary embodiments, information about the stimulation treatment is stored in a memory of the system, for example memory 333 of the console 304. In some embodiments, the information comprises at least one of, stimulation parameter values, muscles affected by the stimulation, information about the contraction of the muscles, input received form the user of the system and / or input received from a trainee. Optionally, the information is stored in a personal card of the trainee. Exemplary stimulation module According to some exemplary embodiments, a system, for example an EMS system comprises one or more stimulation modules. In some embodiments, each stimulation module comprises at least 3 electrodes. In some embodiments, each stimulation module communicates with a central console of the system via wires communication or via wireless communication. Reference is now made to figs. 6A-6D depicting components of a single stimulation module, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a stimulation module 602 comprises at least one control unit 604, and at least 2 separate electrode units, for example electrode units 606, 608 and 610. In some embodiments, each of the control unit 604 and the electrode units comprise at least one electrode through which an electric current can pass into a body, for example into a human body. In some embodiments, each of the separate units 604, 606, 608 and 610 has a separate housing, and is configured to be coupled, optionally removably coupled to an electrode pad 612. According to some exemplary embodiments, each electrode pad 612 has a tissue contacting surface, for example a skin contacting surface coated with an adhesive layer, and a unit contacting surface configured to allow coupling to a unit of the stimulation module. Optionally, the adhesive layer is an electrical conductive adhesive layer. Optionally, two or more units of a stimulation module can be coupled to a single electrode pad, for example to an electrode pad having separate coupling portions at the unit contacting surface. According to some exemplary embodiments, each unit of the stimulation module which comprises an electrode is fixedly coupled to an electrode pad having a replaceable adhesive layer. Alternatively, the unit is removably coupled to an electrode pad, such that the electrode pad is disposable and optionally for single use. 48 According to some exemplary embodiments, for example as shown in fig. 6B, each electrode unit 606, 608 and 610 comprises a PCB assembly 614 optionally comprising an electrode and / or a user interface, for example the electrode 316 and UI 320 shown in fig. 3A. Additionally or optionally, each of the electrode units 606, 608 and 610 comprises a sensing unit module 616, which optionally includes the detector 318 shown in fig. 3A. According to some exemplary embodiments, each of the electrode units 606, 608 and 610 is coupled, for example mechanically and / or electrically, to the control unit 604, for example by a cable 618, optionally a tether cable. Optionally, in some embodiments, at least some of the units are coupled to each other by a cable, in addition or as an alternative to the coupling to the control unit 604. In these embodiments, one or more of the electrode units comprise a power source. According to some exemplary embodiments, the control unit 604 comprises a microcontroller PCB assembly 620, optionally including at least one of the control circuitry 324, the pulse generator 322, the detector 318 and the user interface 320 shown in fig. 3A. In some embodiments, the control unit 604 comprises a power source, for example a battery 622, and a stimulation multiplexer PCB assembly 64, optionally comprises the multiplexer 370 and / or the pulse generator 374 shown in fig. 3B. According to some exemplary embodiments, the control unit 604 further comprises a Bluetooth module 626, for example a Bluetooth low energy (BLE) module, for communicating with other stimulation modules and / or for communicating with a control console of the system, for example console 304 shown in fig. 3A. According to some exemplary embodiments, for example as shown in fig. 6C, each unit of units 604, 606, 608 and 60 has a separate housing, for example housings 630, 632, 634 and 636, respectively. In some embodiments, each of the hosuings comprises a lower electrode coupling surface configured to be coupled to an electrode pad, and an upper opposite surface configured to be visible to a user of the system when the unit is attached to a trainee body. In some embodiments, the control unit 604 comprises a visual indicator 638, for example a light emitting diode (LED) indicator in the upper surface of the housing 630 configured to deliver a visual indication about at least one of, a charging level of an internal power source, for example a battery, of the stimulation module, position of the stimulation module, position of the control unit, and / or activity of the stimulation module during delivery of the stimulation treatment. In some embodiments, each of the units 606, 608 and 610 include a visual indicator which is similar to visual indicator 638, and configured to deliver a visual indication about at least one of, a position of the electrode unit, and / or activity of the electrode unit during delivery of the 49 stimulation treatment. In some embodiments, the upper surface of the unit housings is smooth and curved. In some embodiments, the unit housings are elongated. According to some exemplary embodiments, the lower surface of each of the housings comprises at least one electrode connector, for example at least two spaced apart electrode connectors 640 and 642, electrically coupled to at least one electrode of each unit or to at least two electrodes of a unit. In some embodiments, each of the electrode connectors comprises at least one opening which is shaped and sized to receive an extension of an electrode pad, for securely coupling each unit to an electrode pad. In some embodiments, each of the electrode connectors 640 and 642 is electrically connected to a different electrode of a unit, optionally forming two separate conducting paths of electricity into a subject body by a single unit of the stimulation module. Alternatively, the electrode connectors 640 and 642 are electrically connected to a single electrode, or the connectors 640 and 642 are short circuited, for forming a single conducting path of electricity into the subject body. In some embodiments, one or both of the connectors 640 and 642 are magnetic, for magnetically coupling each of the units to electrode extensions of an electrode pad. According to some exemplary embodiments, a lower surface of a control unit 604, for example as shown in fig. 6D, comprises charging connectors 641 for electrically connecting a power source in the control unit 604 to a charging module. Optionally, the connectors 641 are shaped and sized to fit a matching number of connectors of the charging module. Optionally, the connectors are arranged in a pattern that matches a similar pattern of charging connectors of the charging module. Optionally, each of the electrode units or at least one of the electrode units comprises a power source. In some embodiments, charging of at least one power source of a stimulation module is performed via at least one set of charging connectors located in at least one of the units, for example units 604, 606, 608 and 610. Exemplary stimulation system Reference is now made to fig. 3C depicting a stimulation system, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a stimulation system, for example system 311 comprises one or more stimulation modules, for example 2 stimulation modules, 3 stimulation modules, 4 stimulation modules, 5 stimulation modules, 6 stimulation modules, 7 stimulation modules, 8 stimulation modules, 9 stimulation modules, 10 stimulation modules, 11 stimulation modules, 12 stimulation modules, or any number of stimulation modules, each comprises at least one electrode for delivery of an electric field to a body of a subject. In some 50 embodiments, the stimulation modules, for example stimulation modules 313, 315, 317, 319, 321, 323, 325 and 327, are optionally functionally coupled to at least one control console 329. According to some exemplary embodiments, the control console 329 comprises a memory with a stimulation protocol and / or values of at least one parameter of the stimulation, for example stimulation intensity, stimulation frequency, sequence of stimulation between electrode pairs and / or stimulation modules, stimulation pulse width, stimulation ON time and / or stimulation OFF time. In some embodiments, the console 329 controls the activation of the stimulation modules according to the stimulation protocol or the parameter values. Alternatively, at least one stimulation module serves as a control console and controls the activation of at least some of the other consoles and optionally its own activation as a stimulation module. According to some exemplary embodiments, one or more or all of the stimulation modules of system 311 are functionally coupled to the console 329 wirelessly, by communicating with the console 329 using wireless signals. Alternatively, one or more or all of the stimulation modules of the system 311 are functionally coupled to the console 329 by wires, and communicate with the console 329 by electrical signals delivered by the wires. According to some exemplary embodiments, the system optionally comprises at least one charger, for example charging station 331. In some embodiments, the at least one charger is configured to electrically charge a power source in each stimulation module. In some embodiments, the at least one charger is configured to charge one or more of the stimulation modules, separately and optionally simultaneously. Exemplary electrode pad Reference is now made to figs. 7A-7C, depicting an electrode pad, according to some exemplary embodiments of the invention. According to some exemplary embodiments, an electrode pad 702, also termed herein as electrode patch, comprises a thin and planar body 704 having a tissue contacting surface 706, and an opposite electrode coupling surface 708. In some embodiments, the tissue contacting surface 706 is smooth, and is coated at least partly with an adhesive, for example glue, for adhering the electrode pad to a tissue surface, for example a skin surface. According to some exemplary embodiments, the electrode pad 702 comprises at least two electrical conductors 710 and 712 crossing through the body 704 between the tissue contacting surface 706 and the electrode coupling surface 708. In some embodiments, each of the at least two electrical conductors 710 and 712 have a first planar smooth end 714 in contact with the tissue contacting surface 706, and a second protruding end 716, extending out from the electrode 51 coupling surface 708. In some embodiments, the second protruding end 716, is shaped and sized to penetrate into an opening in connectors 640 and 642 of each unit of a stimulation module, as described in fig. 6D. In some embodiments, a cross section of each protruding end is shaped and sized to fit within an opening in connectors 640 and 642. In some embodiments, the cross section is round. Alternatively, the cross section is oval or polygonal. A potential advantage of having two electrical conductors having two protruding ends extending from the pad body may be to prevent rotation of the electrode pad when coupled to an electrode of a stimulation module. Alternatively, the electrode pad comprises a single electrical conductor, having a protruding extending end having a polygonal cross-section or an asymmetric cross section that fits to penetrate into a matching opening in an electrode connector of the stimulation module. In some embodiments, a distance 720 between the two electrical conductors 710 and 712 is in a range between 12 mm and 21 mm, for example between 12 mm and 17 mm, between 14 mm and 20 mm, between 15 mm and 21 mm, or any intermediate, smaller or larger number value. Optionally, the distance 720 is between 15.5 mm and 17.5 mm , for example about 16.5 mm. In some embodiments, the tissue contacting surface 706 has a surface area between 15cm2 - 50cm2, for example between 20cm2 - 40cm2, between 20cm2 - 30cm2, between 25cm2 - 50cm2, or any intermediate, smaller or larger value. In some embodiments, a thickness 705 of the pad body 704 is between 0.5mm and 5 mm, for example between 0.5 mm and 2 mm, between 1 mm and 1.5 mm, between 1 mm and 3 mm, between 2 mm and 5 mm, or any intermediate, smaller or larger value. According to some exemplary embodiments, the electrical conductors 710 and 712 are formed from an electrical conducting material, for example metal. In some embodiments, the body 704 is formed from a flexible material, for example to allow bending of the electrode pad to conform to anatomy of the subject body. Reference is now made to fig. 7D, depicting layers of an electrode pad, according to some exemplary embodiments of the invention. According to some exemplary embodiments, each electrode pad 750 comprises upper spaced apart electrical conductors 752 and 754, attached to an upper surface of an insulation layer 756. In some embodiments, the insulation layer is formed from an insulating material, for example from Elastane, Thermoplastic elastomers, Rubber based fibers, Neoprene, Polyurethane elastomers, Silver coated fibers, and / or Nonwoven fibers. In some embodiments, the pad body further comprises an intermediate conductive layer 758 formed from a conductive material, for example from Carbon, Conductive hydrogel, Silver, and / or Copper. In some embodiments, the intermediate conductive layer is disposed between the upper insulation layer 756 and a lower hydrogel layer 760. In some embodiments, the hydrogel layer 760 is configured to adhere the electrode pad to a tissue surface, for example to a skin surface. In some embodiments, lower electrical conductors 762 and 764 configured to be placed in contact with tissue, penetrate through the conductive layer 758 an the insulation layer 756 and interlock with the upper conductors 752 and 754, for conducting electricity through layers 756 and 758. According to some exemplary embodiments, an outer tissue contacting surface of the hydrogel layer 760 is coated with a liner layer 766. Exemplary magnetic coupling between an electrode unit and electrode pad According to some exemplary embodiments, each electrode unit is coupled, for example reversibly coupled to an electrode pad. In some embodiments, the electrode unit is magnetically coupled to the electrode pad via at least two connections, for example to prevent rotation of the electrode unit relative to the electrode pad during a stimulation treatment. Reference is now made to figs. 8A and 8B depicting magnetic coupling of an electrode unit to an electrode pad, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a unit 802 having at least one electrode 804, for example a unit of a TMS system, is configured to be magnetically coupled to an electrode pad 806. In some embodiments, the electrical coupling stabilizes an electrical conduction path between the at least one electrode 804 and a tissue surface contacting the electrode pad 806 and via the electrode pad 806. In some embodiments, the unit 802 is similar to the units 604, 606, 608 and 610 shown in figs. 6A-6D or to units 312 and 314 shown in fig. 3A. According to some exemplary embodiments, the unit comprises at least 2 magnetic electrode connectors 808, configured to be coupled, for example reversibly coupled to a metallic portion of the electrode pad 806. In some embodiments, each of the magnetic connectors comprises an opening 810 which is shaped and sized to receive a metallic protrusion on an electric conductor 812 crossing through a body 814 of the electrode pad and extends through a tissue contacting surface 816 of the electrode pad 814. According to some exemplary embodiments, for example as shown in fig. 8B, coupling of the magnetic connectors 808 to the electrical conductors 812 of the electrode pad 806 forms at least one electrical conducting path 814 between the at least one electrode 804 and a tissue 818. 53 Exemplary electric field and unit components Reference is now made to figs. 9A and 9B, depicting generation of at least one electric field between two stimulation units, according to some exemplary embodiments of the invention. According to some exemplary embodiments, each unit of a stimulation module, for example units 604, 606, 608 and 610 shown in figs. 6A-6D or units 312 and 314 shown in fig. 3A, comprises at least one electrode. In some embodiments, coupling of each unit 902 and 904 to an electrode pad 906 and 908 respectively forms at least one electrical conduction path between the at least one electrode 903 and a tissue 910. In some embodiments, for example as shown in fig. 9A and in figs. 8A and 8B, the coupling of at least two magnetic connectors to at least two electrical conductors of an electrode pad, forms two separate electrical conduction paths between a unit and a tissue. According to some exemplary embodiments, for example as shown in fig. 9A each unit of units 902 and 904 comprises at least one magnetic connector for coupling the electrode to an electrode pad, for example to an electrical conductor of an electrode pad. In some embodiments, unit 902 comprises magnetic connectors 906 and 907, each is similar to connector 808 shown in figs. 8A and 8B. As also shown in fig. 8B, the magnetic connectors 905 and 907, each comprising at least one magnet, magnetically couple the electric conductors 933 and 931, respectively. In some embodiments, each magnetic connector is coupled to a single conductor, optionally extending from the electrode pad. In some embodiments, the electrical conductor, for example conductors 931 and 933 of unit 902 and 935 and 937 of unit 904, is similar to electric conductor 812 shown in figs. 8A and 8B. According to some exemplary embodiments, magnetic connectors 921 and 923 of unit 904 are magnetically coupled to electrical conductors 937 and 935, respectively, of electrode pad 908. In some embodiments, the electrical connector penetrates through an opening in the magnetic connector, such that the magnetic connector, optionally a magnet of the magnetic connector, surrounds at least partly the electrical conductor and applies a magnetic field on the electrical conductor. In some embodiments, the electrical conductor, for example conductors 931, 933, 935 and 937 are made from a ferromagnetic material. According to some exemplary embodiments, for example as shown in fig. 9A, when a unit has a single electrode this separate electrical conduction paths are optionally short circuited, for example to deliver a single electric field 911 between the units 902 and 904 and into the tissue 910. In some embodiments, the two separate electrical conduction paths are short circuited in the unit 902 and 904 or in the electrode pad 906. 54 According to some exemplary embodiments, for example as shown in fig. 9B, a unit, for example units 912 and 914 comprise at least two separate electrodes 913 and 915. In some embodiments, at least two electric fields 918 and 920 are delivered between the units 912 and 914, simultaneously or intermittently into the tissue 910. In some embodiments, each of the at least two electric fields is delivered between a different pair of electrodes of units 912 and 914. According to some exemplary embodiments, for example as shown in fig. 9B, each unit of units 912 and 914 comprises at least one position detector 941. In some embodiments, the at least one position detector 941 is located between at least two magnetic connectors, for example magnetic connectors 943 and 945. This is also shown in fig. 9A. In some embodiments, for example as shown in fig. 9A, an electric field 906 is generated and is delivered between the two units 902 and 904 and into the tissue 910. According to some exemplary embodiments, the electric field, for example electric field is 911 is delivered with parameter values that allow penetration of up to 10 cm, for example up to 6 cm, for example up to 4 cm from the tissue surface into the tissue. According to some exemplary embodiments, the delivered electric field, for example electric field 911 affects muscles within a tissue volume 913 through which the electric field 911 travels. Exemplary charging module Reference is now made to figs. 10A and 10B, showing a charging module of a system for stimulating muscles, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a charging module 1002 comprises a body 1004 having a plurality of charging slots, for example pockets 1006, 1008 and 1010 each is sized and shaped to receive a stimulation module of an EMS device. In some embodiments, each stimulation module, for example stimulation module 602 shown in figs. 6A-6D, comprises a control unit and at least 3 electrode units. In some embodiments, each of the pockets 1006, 1008 and 101 is shaped and sized to receive electrodes units of a stimulation module, while a control unit is positioned outside the pocket, for example control units 1012 and 1014, as shown in fig. 10B. According to some exemplary embodiments, the body 1004 comprises a base 1005, configured to allow placing of the charging module on a surface. According to some exemplary embodiments, each control unit is configured to be electrically coupled to charging connectors 1016 and 1018, optionally via magnetic coupling. 55 A potential advantage of keeping the control units outside the pockets may be to allow visualizing a visual indicator of each of the control units, optionally indicating a charging level of each stimulation module. According to some exemplary embodiments, the pockets, for example pockets 1006, 1008 and 1010 are arranged according to anatomical regions, body parts, and / or target locations of the stimulation modules. Optionally, the shape and / or size of the pockets or openings thereof varies to selectively match specific stimulation modules of the EMS system. According to some exemplary embodiments, a width 1009 of an opening of each pocket is between 5 cm and 15 cm, for example, between 5 cm and 10 cm, between 7 cm and 12 cm, between 9 cm and 15 cm, or any intermediate, smaller or larger value. According to some exemplary embodiments, a body 1004 comprises the charging connectors 1016. In some embodiments, each pocket or pocket opening is aligned with a different pair of charging connectors 1016 and 1018 configured to electrically connect a power source to at least one battery of a stimulation module positioned at least partly within a pocket. In some embodiments, the body 1004 comprises at least one magnetic connector adjacent to each pair of charging connectors 1016 and 1018. Alternatively, each pair at least some of the pairs of charging connectors 1016 and 1018 comprise at least one magnetic connector. In some embodiments, the at least one magnetic connector is configured to magnetically couple each pair of charging connectors to charging connectors of a stimulation module. According to some exemplary embodiments, the charging module is configured to electrically charge simultaneously at least 4 stimulation modules each comprising at least one battery and at least 2 electrodes. In some embodiments, during charging, a user interface of each stimulation module is configured to remain outside the pocket, and generates and delivers a visual indication, optionally a color coded indication regarding a charging level of each stimulation module. According to some exemplary embodiments, a casing of a stimulation module comprising the user interface and charging connectors is larger than a pocket opening. According to some exemplary embodiments, a kit comprises at least 4 stimulation modules, for example the stimulation module 602 shown in figs. 6C and 6D, and a charging module 1002. In some embodiments, the kit comprises at least 4, at least 5, at least 6, at least 7, at least 8 stimulation modules, or any larger number of stimulation modules. In some embodiments, the kit comprises a charging module having at least 4 pockets, at least 5 pockets, at least 6 56 pockets, at least 7 pockets, at least 8 pockets, optionally arranged side by side, optionally or additionally in two parallel lines in the body of the charging module. According to some exemplary embodiments, each charging slot is configured to charge a single stimulation module, for example a wireless stimulation module. In some embodiments, a depth of each slot is suitable for covering electrode units of a stimulation module. In some embodiments, a width 1020 of each slot opening is smaller in at least 0.5 cm, in at least 1 cm, in at least 3 cm, in at least 4 cm, from a minimal width 1022 of a control unit of stimulation module, for example control unit 604 shown in figs. 6C and 6D, for example to prevent insertion of the control unit into the slot which allows to keep a user interface of the control unit optionally visual indicator 628 visible during charging. According to some exemplary embodiments, when stimulation modules are positioned at least partly within each charging slot, a distance between two adjacent control units is at least 5 cm, for example to allow insertion of at least one finger between the control units. Optionally, the charging module is configured to allow visualization of control units of at least 4 stimulation modules during charging, for example visualization of control units of at least 5, at least 6, at least 7, at least 8 or any larger number of stimulation modules positioned at least party within the charging slots. Exemplary system user interface Reference is now made to fig. 10C, depicting a graphical user interface of a system for stimulating muscles, for example an EMS system, according to some exemplary embodiments of the invention. According to some exemplary embodiments, the system displays to a user, for example a supervisor of the treatment a graphical interface 1030. In some embodiments, the graphical interface includes a graphical indication 1032 for a position of each stimulation module on a subject body, optionally a distinct color coded indication for each of the stimulation modules. In some embodiments, for each of the stimulation modules, the interface 1030 displays the type of protocol used, name of a body region or muscles group to which the stimulation module is attached, and / or an indication regarding stimulation intensity. Optionally, the interface 1030 allows to increase or decrease values of at least one parameter of the stimulation, for example intensity. In some embodiments, adjusting stimulation parameter values during treatment allows, for example, to adjust the parameter values based on input received from the trainee during 57 treatment. For example, the interface 1030 allows to reduce intensity of stimulation or intensity of the electric field, if current intensity levels cause discomfort or pain. Exemplary simulation modules positioning Reference is now made to fig. 10D depicting positioning of stimulation modules on a body of a human subject, according to some exemplary embodiments of the invention. According to some exemplary embodiments, at least 2 stimulation modules, for example 4 stimulation modules 1040, 1042, 1044, and 1046 are positioned on a subject body 1047. In some embodiments, at least one stimulation module, for example 2 stimulation modules 1040 and 1042, and 2 stimulation modules 1044 and 1046, are positioned on a same side of the body relative to a body midline 1048, above contralateral muscle groups, for optionally achieving a symmetrical exercises of contralateral related muscle groups. For example modules 1042 and 1046 are positioned above the legs, each over a different leg, and modules 1040 and 1044 are positioned above the abdomen, each above a different side of the body. According to some exemplary embodiments, each stimulation module for example module 1040 comprises a control unit 1054 and 3 electrode units, for example units 1052, 1056 and 1058. In some embodiments, after coupling the stimulation modules to the electrode pads, each stimulation module delivers a color coded visual indication which correlates with a color coded indication in the user interface, for example the interface shown in fig. 10C. In some embodiments, the color coded indication indicates that the stimulation module is optionally positioned at a target location and / or is securely coupled to the electrode pads. Exemplary stimulation system setup and preparation Reference is now made to fig. 10E, depicting a setup of a stimulation system, according to some exemplary embodiments of the invention. According to some exemplary embodiments, the stimulation system setup comprises a control console, for example console 1070, a charger 1072 and one or more stimulation modules, for example stimulation modules 1074 and 1076. In some embodiments, for example as shown oin fig. 10E, the stimulation modules are electrically charged by the charger 1072. Optionally, each stimulation module is charged separately from the rest of the stimulation modules, via separate electrical contacts of the charger 1072. According to some exemplary embodiments, the charger 1072 is functionally coupled to the console 1070. In some embodiments, the console 1070 is configured to deliver a human detectable indication, for example a visual and / or an audio indication, about the charging status 58 of each of the stimulation modules. Alternatively or additionally, the charger delivers a human detectable indication about the charging status of the stimulation modules. According to some exemplary embodiments, for example as shown in fig. 10F, a plurality of electrode pads 1080, for example electrode pad 702 shown in figs. 7A-7C, are attached to the skin surface of a subject, at locations selected for delivery of EMS. In some embodiments, once the electrode pads are attached to the skin surface, stimulation modules are coupled to the electrode pads. Exemplary stimulation protocols According to some exemplary embodiments, a muscle stimulation treatment, for example an EMS treatment, comprises a training program of one or more selected muscles group. In some embodiments, the training program comprises one or more training sessions, where in each training session at least one electric field is delivered to the subject body with parameter values suitable for repetitive contract at least one muscle of the one or more muscles groups. In some embodiments, an interval between training sessions lasts between 5 minutes to 1 week, for example between 1 hour to 24 hours, between 12 hours to 48 hours, between 24 hours to 96 hours, between 48 hours and 1 week, or any intermediate, shorter or longer interval time between training sessions, for example consecutive training sessions. Optionally, a single training session on the same muscles group is performed at least every 6 hours, every 24 hours, every 48 hours, every 72 hours, or any intermediate, smaller or larger value.According to some exemplary embodiments, each training session lasts between 10 minutes and 60 minutes, for example between 10 minutes and 40 minutes, between 20 minutes and 40 minutes, between 25 minutes and 25 minutes, or any intermediate, shorter or longer time period of active delivery of at least one electric field to the subject body. In some embodiments, a treatment session lasts about 30 minutes. Optionally a length of a treatment session depends on the stimulated muscle group type and / or number. According to some exemplary embodiments, during a training session, electrodes are stationary positioned on a subject body. In some embodiments, during a training session, at least 3 electrodes, for example 4 electrodes rare coupled to the subject body, optionally stationary positioned on the subject body. According to some exemplary embodiments, the system comprises one or more training protocols, stored for example in a memory 333 of the console 304 shown in fig. 3A. 59 Reference is now made to fig. 11 A, depicting a basic stimulation protocol, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a basic stimulation protocol is optionally used for calibration, for example for personalizing one or more parameters of the electric field delivered to the body of a subject based on information received from the subject and / or information received from a user of the system supervising the training. According to some exemplary embodiments, a training session of the basic protocol is divided into 3 segments. In each segment, the electric field delivered to the body stimulates simultaneously contralateral muscles in a single contraction direction. In some embodiments, stimulation in each segment lasts about 10 minutes. According to some exemplary embodiments, in the basic protocol the electric field has a pulse width between 150ps and 1150ps, for example between 150ps and 300ps, between 200ps and 300ps, between 250ps and 500ps, or any intermediate, smaller or larger value, for example about 250ps. In some embodiments, an electric field frequency is between about 80 Hz and about 100 Hz, for example about 90 Hz. In some embodiments, an ON time in which electric field is delivered is about 6 seconds, and an OFF time in which the electric field is stopped is about 4 seconds. Reference is now made to fig. 11B, depicting an enhanced stimulation protocol, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a training session of the enhanced stimulation protocol is divided into 3 segments. In some embodiments, stimulation in each segment lasts about 10 minutes. In some embodiments, in each segment electric field is delivered via at least 4 electrode pairs in total for both sides of the body, at least two electrode pairs per each side of a body for simultaneously generating contraction of muscle groups at two different directions per a side of a body, optionally using a shared electrode. According to some exemplary embodiments, in the enhanced protocol the electric field has a pulse width between about 150ps and about 1150ps, for example 250ps. In some embodiments, an electric field frequency is between about 30 Hz and about 100 Hz, for example about 35Hz. In some embodiments, an ON time in which electric field is delivered is about 6 seconds, and an OFF time in which the electric field is stopped is about 4 seconds. Reference is now made to fig. 11C, depicting a focused stimulation protocol, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a training session of the focused stimulation protocol is divided into 2 segments. In some embodiments, stimulation in each segment lasts 60 about 15 minutes. In some embodiments, in each segment electric field is delivered via at least 4 electrode pairs in total for both sides of the body, at least two electrode pairs per each side of a body for simultaneously generating contraction of muscle groups at two different directions and in a single direction per a side of a body, optionally using a shared electrode. According to some exemplary embodiments, in the enhanced protocol the electric field has a pulse width between about 150ps and about 1150ps, for example 250ps. In some embodiments, an electric field frequency is between about 30 Hz and about 100 Hz, for example about 50Hz. In some embodiments, an ON time in which electric field is delivered is about 6 seconds, and an OFF time in which the electric field is stopped is about 4 seconds. Reference is now made to figs. 11D-11G, depicting a protocol for a plyometric exercise, for example for a full body plyometric exercise, according to some exemplary embodiments of the invention. According to some exemplary embodiments, a plyometric exercise involves short, intense bursts of activity that optionally target fast-twitch muscle fibers. According to some exemplary embodiments, for example a shown in fig. 11D, a plyometric protocol of the front body comprises positioning two stimulation modules having 4 electrodes each at the abdomen region at both contralateral sides of the body, and two stimulation modules, one on each leg. In some embodiments, the front body plyometric protocol is divided into 3 stages, during each stage a burst of electric field is delivered for 2 seconds. In some embodiments, during the protocol sequence the abdomen region and the legs, each are stimulated for 4 seconds followed by relaxation of 2 seconds, where during stage 2 both the abdomen and the legs are contracted. In some embodiments, during the protocol an abdomen region and a legs region, in each side of the body is stimulated by 4 different pairs of electrodes using two shared electrodes for generating simultaneous contraction of muscles at different directions. Fig. HE shows a stimulation sequence between the different regions, according to some exemplary embodiments of the invention. In some embodiments, the stimulation sequence is repeated for about 30 minutes, where each stage lasts about 2 seconds. According to some exemplary embodiments, in the plyometric protocol of the front and back body the delivered electric field has a pulse width between about 150ps and about 1150ps, for example about 300ps. In some embodiments, an electric field frequency is between about 30 Hz and about 100 Hz, for example about 50Hz. According to some exemplary embodiments, for example a shown in fig. 11F, a plyometric protocol of the back body comprises positioning two stimulation modules having 4 electrodes each above glutes muscles region at each contralateral side of the body, and two 61 stimulation modules, one above a thighs region of each leg. In some embodiments, the back body plyometric protocol is divided into 3 stages, during each stage a burst of electric field is delivered for about 2 seconds. In some embodiments, during the protocol sequence the glutes and thigh regions, each is stimulated for 4 seconds followed by a relaxation period of 2 seconds, where during stage 2 both the glutes and the thighs are contracted. In some embodiments, during the protocol the glutes region and the thighs region, in each side of the body is stimulated by 4 different pairs of electrodes using two shared electrodes, one at each stage, for generating simultaneous contraction of muscles at different directions. Fig. 11G shows a stimulation sequence between the different regions, according to some exemplary embodiments of the invention. In some embodiments, the stimulation sequence is repeated for about 30 minutes, where each stage lasts about 2 seconds. According to some exemplary embodiments, in the plyometric protocol of the back body the delivered electric field has a pulse width between about 200ps and about 400ps, for example about 300ps. In some embodiments, an electric field frequency is between about 40 Hz and about 60 Hz, for example about 50Hz. Exemplary electrodes positioning and stimulation setup According to some exemplary embodiments, in order to deliver an electric field to selected muscles, at least two electrodes are positioned in a close proximity to the muscles. Optionally, the electrodes are attached to a skin surface above the selected muscles. In some embodiments, a distance between a pair of electrodes through which the electric field is delivered is adjusted according to electric field parameters and / or distance from a target muscle or target muscle group. Alternatively, the electric field parameters are adjusted according to a distance between the two electrodes and / or distance from the target muscle or target muscle group. According to some exemplary embodiments, the electrodes are electrodes of a stimulation module, for example stimulation module 602 shown in in figs. 6A-6D, electrically coupled to electrode pads, for example electrode pad 702 shown in figs. 7A-7C. In some embodiments, each electrode of a stimulation module is coupled to an electrode pad comprising electrical conductors. Reference is now made to figs. 12A-12H depicting body locations, for example anatomical body locations, for positioning of electrodes on a subject body, according to some exemplary embodiments of the invention. According to some exemplary embodiments, for example as a shown in fig 12A, at least 2 electrodes, for example 4 electrodes 0-3 are position over a right abdomen region 1202, and at 62 least 2 electrodes, for example 4 electrodes 0-3 are positioned over a left abdomen region 1204. In some embodiments, the first group of 4 electrodes positioned at region 1202 are part of a first stimulation module, and the second group of 4 electrodes positioned at region 1204 are part of a second stimulation module. In some embodiments, the electrodes positioned at the right abdomen region 1202 are used to stimulate one or more muscles of the right abdomen. In some embodiments, the electrodes positioned at the left abdomen region 1204 are used to stimulate one or muscles of the left abdomen. According to some exemplary embodiments, at least 2 electrodes, for example 4 electrodes 0-3 are positioned over the right upper leg region 1206, for example to stimulate quadriceps muscles of the right leg. In some embodiments, the electrodes at region 1206 are part of a single stimulation module. According to some exemplary embodiments, at least 2 electrodes, for example 4 electrodes 0-3 are positioned over the left upper leg region 1208, for example to stimulate quadriceps muscles of the left leg. In some embodiments, the electrodes at region 1208 are part of a single stimulation module. According to some exemplary embodiments, in order to stimulate muscles of the arms, 4 electrodes of a stimulation module are coupled to a right arm, and 4 electrodes of a different stimulation module are coupled to a left arm, for example as shown in figs. 12C and 12D. In some embodiments, 2 electrodes of a stimulation module are positioned over front hand muscles at region 1209, and 2 electrodes of the same stimulation module are positioned over back hand muscles at region 1210, of the left side of the subject body. In some embodiments, 2 electrodes of a different stimulation module are positioned over front hand muscles at region 1212, and 2 electrodes of the same stimulation module are positioned over back hand muscles at region 1214, of the left side of the subject body. In some embodiments, electrodes over front hand muscles, at regions 1209 and 1212 are used to stimulate arms biceps, and electrodes over back hand muscles, at regions 1210 and 1214 are used to stimulate arms triceps. According to some exemplary embodiments, stimulation is synchronized between stimulation modules such that stimulation is delivered by a first stimulation module to biceps muscles at a first side of a body, while stimulation is delivered by a second stimulation module to triceps muscles at a second side of the body. According to some exemplary embodiments, for example as shown in fig. 12E, in order to stimulate trapezius muscles, electrodes, for example electrodes of a first stimulation module, are positioned over trapezius muscles of the left side of the back at region 1214, and optionally, 63 different electrodes, for example electrodes of a second stimulation module, are positioned over trapezius muscles of the right side of the back, at region 1216. According to some exemplary embodiments, for example as shown in fig. 12F, in order to stimulate muscles of the back, electrodes, for example electrodes of a first stimulation module, are positioned over back muscles of the left side of the back at region 1218, and optionally, different electrodes, for example electrodes of a second stimulation module, are positioned over back muscles of a right side of the back at region 1220. In some embodiments, electrodes of the first stimulation module and electrodes of the second stimulation module can stimulate back muscles of the two sides of the back simultaneously, or alternately. Optionally, at least two stimulation modules can be electrically connected, for example to allow delivery of an electric field between an electrode of a first stimulation module and an electrode of a second stimulation module. According to some exemplary embodiments, for example as shown in fig. 12G, in order to stimulate gluteal muscles, electrodes, for example electrodes of a first stimulation module, are positioned over gluteus muscles of the left buttocks at region 1222, and optionally, different electrodes, for example electrodes of a second stimulation module, are positioned over gluteus muscles of a right buttocks at region 1224. According to some exemplary embodiments, for example as shown in fig. 12H, in order to stimulate hamstrings muscles, electrodes, for example electrodes of a first stimulation module, are positioned over hamstrings of a left leg at region 1226, and optionally, different electrodes, for example electrodes of a second stimulation module, are positioned over hamstrings muscles of a right leg at region 1228. According to some exemplary embodiments, for example as shown in fig. 121, in order to stimulate calves muscles, electrodes, for example electrodes of a first stimulation module, are positioned over calves of a left leg at region 1230, and optionally, different electrodes, for example electrodes of a second stimulation module, are positioned over calves of a right leg at region 1232. According to some exemplary embodiments, parameter values of an electric field delivered to muscles are adjusted according to the muscles to be stimulated and / or position of electrodes relative to each other and / or relative to the target muscles. Table A below provides exemplary ranges of parameter values of an electric field pulse for stimulating specific muscle groups, according to some exemplary embodiments of the invention: Muscles group Phase duration [psec] Frequency [Hz] Arms about 100-about 300 about 50-about 150 Abdominal about 250-about 500 about 50-about 100 Quadriceps about 250-about 500 about 50-about 100 Trapezius about 200-about 400 about 30-about 75 Back about 250-about 500 about 30-about 75 Gluteus about 250-about 500 about 50-about 100 Hamstrings about 250-about 500 about 50-about 100 Calves about 200-about 400 about 20-about 100 It should be understood that optionally different phase durations between 50 psec and 500 psec, and optionally different frequency values between 1Hz to 150Hz can be used to deliver an electric field to one or more of the muscles groups described in Table A. According to some exemplary embodiments, an intensity of the electric field delivered between at least 2 electrodes is up to 80 milliamper (mA), for example up to 70mA, up to 60mA, up to 55mA, or any intermediate, smaller or larger value. Optionally, the intensity is adjusted according to pain sensation threshold of a subject, to be lower than the pain sensation threshold. Exemplary exercises According to some exemplary embodiments, the system, for example one or more stimulation modules of the system are used to contract one or more muscles as part of an exercise. In some embodiments, the system is used to emulate known muscles exercises by delivery of an electric field to the muscles. In some embodiments, the system is used to simultaneously contract at least two adjacent muscles oriented at different directions, using at least 3 electrodes, for example by delivery electric fields by at least two pairs of electrodes having at least one shared electrode, in alternation, while keeping the at least two adjacent muscles contracted. According to some exemplary embodiments, the system comprises at least one stimulation module which includes at least 3 electrodes. In some embodiments, the system delivers an exercise to muscles at different body parts using at least 2 stimulation modules, for example 2, 3, 4, 5, 6, 7, 8, 9, 10 or any larger number of stimulation modules. According to some exemplary embodiments, the system synchronizes the delivery of an electric field between at least two electrode pairs of a single stimulation module and / or between electrode pairs of different stimulation modules, according to an exercise protocol. In some embodiments, a control unit, for example a control circuitry, functionally coupled to at least two stimulation modules, synchronizes muscle stimulation between two sides of the body, for example when each of the at least two stimulation modules is coupled to a different side of the 65 body, a left side and a right side. Alternatively, or additionally, the control unit, synchronizes delivery of electric fields between two electrode pairs of the same stimulation module, a first electrode pair positioned over front muscles of a body portion, for example over biceps muscles of the arm, and a second electrode pair positioned over back muscles of the body portion, for example over triceps muscles of the arm. A potential advantage of delivery of electric fields in synchronization between a plurality of electrode pairs, positioned at different locations on the subject body, for example using at least 10 electrodes, may be to allow delivering of a physical exercise to different body parts, for example upper and lower body and to two sides of the body, without a need to reposition electrodes or change the number of electrodes attached to the body, optionally as part of a single EMS exercise. According to some exemplary embodiments, the system is used to deliver an exercise which combines activation of: abdominal internal muscles, abdominal external muscles, Quadriceps internal muscles group, and Quadriceps external muscles group, in both sides of the body, optionally using 4 stimulation modules each comprising 4 electrodes. In some embodiments, 2 stimulation modules are positioned over abdominal muscles (both sides of the abdomen), and 2 stimulation modules are positioned over quadriceps muscles (both legs). The system delivers the exercise in a sequence that stimulates and contracts the muscles as in a deadlift exercise. Optionally, the exercise is a plyometric exercise, delivered via EMS. In some embodiments, the exercise is delivered in 3 stages, each lasts about 10 minutes for a total time period of about 30 minutes. In some embodiments, in each side of the body, stimulation of Quadriceps muscles and abdominal muscles is performed by delivery of stimulation via electrode pairs having at least one shared electrode, and intermittently at different directions to contract two neighboring muscles oriented in an angle relative to each other, within the same time window. According to some exemplary embodiments, the system is used to deliver an exercise which combines activation, for example contraction, of: arms triceps, arm biceps, Quadriceps internal muscles group, and Quadriceps external muscles group, in both sides of the body, optionally using 4 stimulation modules, each comprising 4 electrodes. In some embodiments, 2 stimulation modules are positioned over arms of the subject (one for each arm), and 2 stimulation modules are positioned over quadriceps muscles (both legs). The system delivers the exercise in a sequence that stimulates and contracts the muscles as in a step up single leg balance with bicep curl exercise. Optionally, the exercise is a plyometric exercise, delivered via EMS. In some embodiments, the exercise is delivered in 3 stages, each lasts about 10 minutes for a total time period of about 30 minutes. In some embodiments, in each side of the body, stimulation of 66 Quadriceps muscles is performed by delivery of stimulation via electrode pairs having at least one shared electrode, and intermittently at different directions to contract two neighboring muscles oriented in an angle relative to each other, within the same time window. In some embodiments, the stimulation modules for stimulating the arms are positioned in regions 1209 and 1214, and in regions 1212 and 1210, as shown in figs. 12C and 12D. According to some exemplary embodiments, the system is used to deliver an exercise which combines activation, for example contraction, of: Buttocks internal muscles group, Buttocks external muscles group, Hamstrings internal muscles group and Hamstrings external muscles group, in both sides of the body, optionally using 4 stimulation modules, each comprising 4 electrodes. In some embodiments, 2 stimulation modules are positioned over the Buttocks (one per each side), and 2 stimulation modules are positioned over Hamstrings muscles (one for each leg). Optionally, the exercise is a plyometric exercise, delivered via EMS. In some embodiments, the exercise is delivered in 3 stages, each lasts about 10 minutes for a total time period of about 30 minutes. In some embodiments, in each side of the body, stimulation of each muscle group is performed by delivery of stimulation via electrode pairs having at least one shared electrode, and intermittently at different directions, to contract two neighboring muscles oriented in an angle relative to each other, within the same time window. Reference is now made to figs. 13A-13D depicting an EMS exercise for a workout of arm muscles in synchronization with abdominal muscles, according to some exemplary embodiments of the invention. According to some exemplary embodiments, the system is used for delivery of at least one exercise which includes stimulation of both abdominal muscles and arms muscles, optionally emulating a standing medicine ball chest pass exercise. In some embodiments, for example as shown in figs. 13A and 13B, at least two stimulation modules each with at least 4 electrodes are positioned over arms of a trainee. In some embodiments, at least one first stimulation module is coupled to a left arm, and at least one second stimulation module is coupled to a right arm of the trainee. In some embodiments, for example as shown in fig. 13A, two electrodes of each stimulation module, for example electrodes 1 and 2, are positioned over triceps muscles of each arm, and two electrodes, for example electrodes 0 and 3 are positioned over biceps muscles of each arm. Additionally, for example as shown in figs. 13C and 13D, at least 4 electrodes, optionally of a first stimulation module, are coupled to a left abdominal region, and at least 4 different electrodes, optionally of a different stimulation module, are coupled to a right abdominal region, of the trainee. 67 According to some exemplary embodiments, during the exercise, electrodes positioned on the arm, for example electrodes 1 and 2 of a stimulation module are used to deliver a first electric field with parameter values suitable to contract triceps muscles, and electrodes 0 and 3 of the stimulation module are used to deliver a second electric field with parameter values suitable to contract biceps muscles. Additionally, for example as shown in figs. 13C and 13D, electrodes positioned over the abdomen region are used to deliver two electric fields in alternation between two electrode pairs having a shared electrode, with parameter values suitable to contract internal abs muscles (13C), and two different electric fields in alternation between two different electrode pairs having a shared electrode, with parameter values suitable for contracting external abs muscles (13D). According to some exemplary embodiments, an EMS exercise duration is at least about 5 minutes, for example at least about 10 minutes, at least about 20 minutes, or any intermediate, shorter time duration. According to some exemplary embodiments, an exercise which involves muscle groups located at different body regions is divided into at least 2 separate stages. In some embodiments, for example as shown in fig. 13E, the exercise which involves stimulation of both arms muscles and abdomen muscles, is divided into 3 separate stages, for example stage 1, stage 2 and stage 3. In some embodiments, in each stage, different muscle groups are stimulated according to the sequence of in the standing medicine ball chest pass exercise. Optionally, a warmup session in which stimulation is delivered to the muscles for short time periods of up to about 5 seconds, up to about 4 seconds, up to about 3 seconds, up to about 2 seconds, or any intermediate, shorter or longer time period, is performed in the beginning of the exercise, for example in the beginning of the first stage, and optionally as part of the first stage. In some embodiments, the warmup session is part of the first stage. Optionally, the warmup session lasts for up to about 4 minutes, up to about 3 minutes, up to about 2 minutes, up to about 1 minutes, or any intermediate, shorter or longer time period. Optionally, the warmup session is performed in the beginning of each stage. According to some exemplary embodiments, each of the 3 stages lasts for about 10 minutes. In some embodiments, during the first stage, a stimulation sequence of 6 seconds comprises, stimulation of arms triceps for about 2 seconds at block 1302, followed by stimulation, optionally simultaneous stimulation, of arms biceps and internal abdominal muscles for about 2 seconds at block 1304, followed by stimulation of external abdominal muscles for about 2 seconds, at block 1306. In some embodiments, the stimulation sequence of the first stage is repeated for an overall time period of about 10 minutes. 68 According to some exemplary embodiments, during the second stage (stage 2), the stimulation sequence of stage 1 is repeated in 3 separate blocks, 1308, 1310 and 1312, each lasts about 6 seconds, for an overall sequence duration of about 18 seconds. In some embodiments, the stimulation sequence is repeated up to a total time duration of about 10 minutes. According to some exemplary embodiments, stage 3 of the exercise is similar to stage 1. Reference is now made to fig. 14, depicting an EMS protocol focusing on abdominal muscles, according to some exemplary embodiments of the invention. According to some exemplary embodiments, at least two stimulation modules are positioned over an abdomen region of a trainee body, one per each side of the abdomen. In some embodiments, each stimulation module comprises 4 electrodes, 0-4, attached to the subject body in different locations over abdomen muscles. According to some exemplary embodiments, the electrodes are used to deliver an abdomen muscle EMS workout, which includes 3 stages, each stage emulates a different exercise involving abdominal muscles groups. In some embodiments, the EMS protocol is divided into a warmup stage, which lasts about 2 minutes, a first stage 1404 which lasts between about 8 minutes to about 10 minutes, a second stage 1406 which lasts about 10 minutes and a third stage 1408 which lasts about 10 minutes. According to some exemplary embodiments, during a warmup stage 1402, electric fields are delivered with a frequency of about 100 Hz between electrodes 0 and 1 at the left side of the abdomen, and between electrodes 0 and 3 at the right side of the abdomen for 2 seconds, followed by delivery of electric fields between electrodes 2 and 3 at the left side of the abdomen, and between electrodes 1 and 2, at the right side of the abdomen for 2 seconds, followed by 2 seconds OFF stimulation (no electric field delivery), within a stimulation sequence of 6 seconds. In some embodiments, the stimulation sequence is repeated during about 2 minutes of the warmup stage 1402. According to some exemplary embodiments, the warmup stage, for example stage 1402 is used for calibrating an intensity of the electric field according to a pain sensation threshold of the trainee. In some embodiments, the intensity level is adjusted to an intensity of up to 70mA, for example up to 60mA, up to 51mA, up to 40mA, or any intermediate, smaller or larger intensity value. In some embodiments, the warmup stage 1402 is used to validate positions of the electrodes, to make sure that dlivery of an electric field between electrode pairs stimulates, for example contracts, specific muscles and / or specific muscle groups, for example muscles of the abdomen region. According to some exemplary embodiments, the first stage 1406 is used to deliver an electric field with parameter values suitable to contract oblique abdomen muscles and Rectus Abdominis muscles of the abdomen, at both sides of the abdomen and optionally simultaneously. In some embodiments, the delivered electric field contracts the muscle groups in a sequence of 6 seconds ON (active delivery of an electric field), followed by 6 seconds OFF (no electric field delivery), optionally followed by 6 seconds of active rest which includes 3 seconds of ramp up to maximal intensity and 3 seconds of ramp down to zero intensity. In some embodiments, the sequence of the first stage emulates an Ab crunch exercise. In some embodiments, the sequence of the first stage is repeated for about between 8 minutes and about 10 minutes. According to some exemplary embodiments, the second stage 1406 is used to deliver an electric field with parameter values suitable to contract oblique abdomen muscles and Rectus Abdominis muscles of the abdomen, at both sides of the abdomen and optionally simultaneously, in a sequence optionally designed to emulate contraction of the muscles during a medicine ball twist exercise. In some embodiments, in the first block of the stage, an electric field is delivered between electrodes 1,2 and 3 in the right side, intermittently between a first pair of electrodes 2 and 3, and a second pair of electrodes 1 and 2, using electrode 2 as a shared electrode, for inducing contraction of a long oblique muscle. In some embodiments, within the same time window, optionally simultaneously, an electric field is delivered via electrodes 0 and 1 of the left side to contract a rectus abdominis muscle of the left side of the abdomen. In some embodiments, during the first block, an electric field is delivered for a time period of 4 seconds. In some embodiments, in the second block an electric field is delivered by electrodes 0 and 3 to contract a rectus abdominis muscle of the left side of the abdomen, and by electrodes 1,2 and 3, using electrode 2 as a shared electrode, to contract a long oblique muscle of the left side of the abdomen. In some embodiments, during the second block, an electric field is delivered for a time period of 4 seconds, intermittently with the first block for a total time period of the second stage 1406 of 10 minutes. According to some exemplary embodiments, the third stage 1406 is used to deliver an electric field with parameter values suitable to contract oblique abdomen muscles and Rectus Abdominis muscles of the abdomen, at both sides of the abdomen and optionally simultaneously, in a sequence optionally designed to emulate contraction of the muscles during a crunch and twist exercise. In some embodiments, in a first block of the third stage, electric fields are delivered between electrodes 0 and 1, and between electrodes 2 and 3 at the left abdomen, and between 70 electrodes 0 and 3, and between electrodes 1 and 2 at the right abdomen for about 4 seconds. Optionally, electric fields are delivered by electrodes at the left abdomen and at the right abdomen, intermittently, for about 4 seconds ON, and about 4 seconds OFF. In some embodiments, in the second block, an electric field is delivered between 5 electrodes 1,2 and 3 (using electrode 2 as a shared electrode) at the left abdomen, and electrodes 0 and 3 at the right abdomen, optionally simultaneously, for a time period of 2 seconds. In some embodiments, in the third block, an electric field is delivered between electrodes 1,2, and 3 at the right abdomen, and electrodes 0 and 1 at the left abdomen, optionally simultaneously, for a time period of 2 seconds. In some embodiments, the stimulation sequence 10 following the second and third blocks includes a 2 seconds OFF period (no electric field delivery). In some embodiments, a sequence which includes the second block, the third block and the OFF period (total of 6 seconds) is repeated 4 times, within an overall sequence of the third stage 1408, which is repeated for a time period of about 10 minutes overall. Table B below describes exemplary electric field parameters for stimulating muscles, in 15 the exercise shown in fig. 14, per each exercise segment, for muscles of the left body (electrodes Al and A2 represents a first pair of electrodes, and electrodes Bl and B2 represent a second electrode pair): # Segment Electrode Al Electrode A2 Electrode Bl Electrode B2 Burst Duration [sec] Phase duration [psec] Frequency [Hz] 1 Warm up [2min] 0 1 NA NA 2 300 100 2 3 NA NA 2 300 100 Break for 2 sec 2 Abdominal Crunches [8min] 0 1 2 3 6 300 100 Break for 6 sec 3 Medicine Ball Twist [lOmin] 1 2 2 3 4 300 100 0 3 NA NA 4 300 100 Break for 4 sec 4 Crunch and Twist [lOmin] 0 1 2 3 4 300 100 Break for 4 sec 1 2 2 3 2 300 100 0 3 NA NA 2 300 100 Break for 2 sec According to some exemplary embodiments, electrodes can be placed over muscles of the Buttocks, for example to provide stimulation that optionally emulates Buttocks muscles workout. In some embodiments, at least 4 electrodes are positioned over Buttocks muscles of the left side of the body, and at least 4 different electrodes are positioned over Buttocks muscles of the right side of the body. Optionally, each group of at least 4 electrodes is part of a stimulation module, such that a first stimulation module is placed over left Buttocks muscles and a second stimulation module is placed over right Buttocks muscles. In some embodiments, a stimulation protocol, for example a first stimulation protocol is used to deliver electric fields between different electrode pairs to emulate contraction sequence of muscles as in a hip extension exercise. Alternatively or additionally, a second stimulation protocol is used to deliver electric fields between different electrode pairs to emulate contraction sequence of muscles as in a single leg press exercise. Alternatively or additionally, a third stimulation protocol is used to deliver electric fields between different electrode pairs to emulate contraction sequence of muscles as in a lever good morning hack squat exercise. According to some exemplary embodiments, electrodes positioned over the quadriceps of both legs, for example at least 4 electrodes for each leg), are used to deliver one or more stimulation protocols, optionally to emulate a sequence of quadriceps muscles contraction as in a squat exercise, a Cossack squats exercise, and / or a squat and pulsing exercise. According to some exemplary embodiments, electrodes positioned over the hamstrings muscles of both legs, for example at least 4 electrodes for each leg), are used to deliver one or more stimulation protocols, optionally to emulate a sequence of hamstrings muscles contraction as in a lying leg exercise, a standing single leg curl exercise, and / or a leg curl on stability ball exercise. According to some exemplary embodiments, electrodes positioned over abdomen muscles, for example at least 4 electrodes for each abdomen side), are used to deliver one or more stimulation protocols, optionally to emulate a sequence of abdomen muscles contraction as in a crunch and twist exercise, a lower ab cross scissors exercise, and / or a leg raise with twist exercise. According to some exemplary embodiments, electrodes positioned over buttocks muscles, for example at least 4 electrodes at each side of the body), are used to deliver one or more stimulation protocols, optionally to emulate a sequence of buttocks muscles contraction as in a 72 lever good morning hack squat exercise, a single leg glute bridge exercise, and / or a lever good morning hack exercise. According to some exemplary embodiments, electrodes positioned over the quadriceps of both legs, for example at least 4 electrodes for each leg), are used to deliver one or more stimulation protocols, optionally to emulate a sequence of quadriceps muscles contraction as in a squat and pulsing exercise, a walking lunges Cossack squats exercise, and / or a single leg step up exercise. According to some exemplary embodiments, electrodes positioned over the hamstrings muscles of both legs, for example at least 4 electrodes for each leg), are used to deliver one or more stimulation protocols, optionally to emulate a sequence of hamstrings muscles contraction as in a leg curl on stability ball or a lying leg curl exercise, an inverse leg curl with bench exercise, and / or a leg curl on stability ball exercise. According to some exemplary embodiments, electrodes positioned over abdomen muscles, for example at least 4 electrodes for each abdomen side), are used to deliver one or more stimulation protocols, optionally to emulate a sequence of abdomen muscles contraction as in a leg raised with twist exercise, a side plank pull exercise, and / or a front plank side hop exercise. According to some exemplary embodiments, electrodes positioned over the quadriceps of both legs, for example at least 4 electrodes for each leg, are used to deliver one or more stimulation protocols, optionally to emulate a sequence of quadriceps muscles contraction as in a single leg set up exercise, a walking curtsy lunge exercise, and / or a single leg step up exercise. According to some exemplary embodiments, electrodes positioned over the each arm, for example at least 4 electrodes for each arm optionally of a single stimulation module, are used to deliver one or more stimulation protocols to contract biceps and triceps muscles of each arm, optionally to emulate a sequence of arm muscles contraction as in an incline bicep curl exercise, a triceps push down exercise, a hammer curl to triceps kickback exercise, an incline alternate biceps curl exercise, an incline triceps kickback exercise, and / or a dumbbell biceps curl with overhead extension exercise. According to some exemplary embodiments, electrodes positioned over a specific body region, for example electrodes of at least one stimulation module, are used to deliver electric fields with parameter values suitable to contract 2,3,4 or any larger number of different muscles in the body region, for a time period between 2 minutes and 60 minutes, for example a time period between 5 minutes and 20 minutes, a time period between 10 minutes and 40 minutes, a time period between 25 minutes and 35 minutes, or any intermediate, shorter or longer time 73 period, while electrodes remain attached to the subject body during the entire stimulation time period, for example without repositioning of the electrodes on the subject body. Exemplary face stimulation According to some exemplary embodiments, the system is used to stimulate muscles of the face, using at least 3 electrodes, for example 3,4,5,6,7,8,9,10 electrodes or any larger number of electrodes. Optionally, the at least 2 electrodes are part of a facemask. In some embodiments, the electrodes are used to deliver multidirectional bursts of electric fields, optionally up to 3, up to 4, up to 5, up to 6 or any larger number of bursts in parallel. According to some exemplary embodiments, the stimulation, for example EMS, is delivered to facial muscles, as part of a cosmetic procedure for reduction of wrinkles, to improve skin tone, to improve facial symmetry, and / or to enhance facial contour. Alternatively, or additionally, the stimulation is delivered as part of a rehabilitation procedure or treatment, for example to treat muscle atrophy, Bell’s palsy, facial asymmetry, to assist in post-surgical recovery or stroke recovery, and / or to reduce symptoms of Temporomandibular Joint Disorder (TMD). Reference is now made to fig. 15, depicting positioning of electrodes over facial muscles, according to some exemplary embodiments of the invention. According to some exemplary embodiments, two or more electrodes are positioned on a subject face 1502, over one or more facial muscles. In some embodiments, at least 2 electrodes, for example electrodes 1504 and 1506 are positioned on a forehead. In some embodiments, at least 2 electrodes are positioned over orbital regions of the face, for example electrodes 1508 and 1510. In some embodiments, at least 2 electrodes are positioned over upper oral muscles. For example, electrodes 1512 and 1514. In some embodiments, at least 2 electrodes are positioned over lower oral muscles, for example electrodes 1516 and 1518. According to some exemplary embodiments, electric fields are delivered between electrodes 1512 and 1516, and between electrodes 1518 and 1514, optionally with parameter values suitable to contract side face muscles. In some embodiments, an electric field is delivered between electrodes 1516 and 1518, for example to contract at least one muscle of the chin region, mentalis muscles and / or depressor labii inferioris muscles. According to some exemplary embodiments, electric fields are delivered between electrodes 1504 and 1508, and between electrodes 1506 and 1510, to contract one or both of, at least one procers muscle, at least one corrugator supercili muscle, of the face. In some 74 embodiments, an electric field is delivered between electrodes 1504 and 1506 to contract at least one frontal belly (frontalis) of epicranius muscle, of the face. According to some exemplary embodiments, the electrodes, for example electrodes 1504, 1506, 1508, 1510, 1512, 1514, 1516, and 1518, are part of a stimulation mask 1520, for example an EMS stimulation mask. In some embodiments, the mask comprises at least one fastener, for example an elastic band, for attaching the mask and the electrodes to the face of the subject. Alternatively, or additionally, the mask comprises an adhesive, for example an adhesive layer on a surface configured to be in contact with the face, for reversibly adhering the mask and the electrodes to the face of the subject. In some embodiments, the mask 1520 comprises one or more of the components of a stimulation module, for example the stimulation module 602 shown in figs. 6A-6D, or the stimulation module 308 shown in fig. 3A. According to some exemplary embodiments, the mask comprises adjustable portions, for example to adjust a distance between electrodes, and / or to better fit the mask to faces sizes. Alternatively, different masks are preformed, at different sizes, for example to better fit different face sizes. As used herein with reference to quantity or value, the term “about” means “within ± 10 % of’. The terms “comprises”, “comprising”, “includes”, “including”, “has”, “having” and their conjugates mean “including but not limited to”. The term “consisting of’ means “including and limited to”. The term “consisting essentially of’ means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure. As used herein, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof. Throughout this application, embodiments of this invention may be presented with reference to a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as “from 1 to 6” should be considered to have specifically disclosed subranges such as “from 1 to 3”, “from 1 to 4”, “from 1 to 5”, “from 75 2 to 4”, “from 2 to 6”, “from 3 to 6”, etc.; as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. Whenever a numerical range is indicated herein (for example “10-15”, “10 to 15”, or any pair of numbers linked by these another such range indication), it is meant to include any number (fractional or integral) within the indicated range limits, including the range limits, unless the context clearly dictates otherwise. The phrases “range / ranging / ranges between” a first indicate number and a second indicate number and “range / ranging / ranges from” a first indicate number “to”, “up to”, “until” or “through” (or another such range-indicating term) a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numbers therebetween. Unless otherwise indicated, numbers used herein and any number ranges based thereon are approximations within the accuracy of reasonable measurement and rounding errors as understood by persons skilled in the art. As used herein the term “method” refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts. As used herein, the term “treating” includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition or delivering a cosmetic non-therapeutic treatment or a muscles training to a healthy subject. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, 5 citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is / are hereby incorporated herein by reference in its / their entirety.

Claims

1. A method for providing a plyometric exercise to a subject, comprising:selecting at least one target region of interest (ROI) in a subject body for a plyometric exercise;positioning at least 2 electrodes above a tissue volume at said selected target ROI;generating at least one electric field by at least one pulse generator electrically coupled to said at least 2 electrodes;delivering said at least one electric field between said at least 2 electrodes to said tissue volume with parameter values selected for contracting at least one muscle in said tissue volume as part of a plyometric exercise of said at least one muscle.

2. A method according to claim 1, wherein said delivering comprises delivering said at least one electric field with parameter values selected for inducing rapid movement between contraction and relaxation of the at least one muscle.

3. A method according to any one of claims 1 or 2, wherein said delivering comprises delivering short repetitive bursts of said at least one electric field between said at least 2 electrodes and into the tissue volume, wherein each burst of said short repetitive bursts lasts for up to 4 seconds, and wherein an interval between two consecutive short repetitive bursts is up to 8 seconds.

4. A method according to any one of the previous claims, wherein said selecting comprises selecting at least two spaced apart region of interests (ROIs) in a subject body for a plyometric exercise, wherein said positioning comprises positioning at least two pairs of electrodes, each above a tissue volume at a different ROI of said at least two spaced apart ROIs, and wherein said delivering comprises delivering a first electric field between a first pair of electrodes of said at least two pairs of electrodes, and a second electric field between a second pair of electrodes of said at least two pairs of electrodes, in synchronization with the delivery of said first electric field, according to predetermined timing.

5. A method according to claim 4, wherein said predetermined timing is selected for contracting in parallel or in a sequence at least one first muscle in a tissue volume of a first ROI of said at least two spaced apart region of interests (ROIs) by said first electric field, and at least one second muscle in a different tissue volume of a second ROI by said second electric field.

6. A method according to any one of claims 4 or 5, wherein each of said at least two spaced apart region of interests (ROIs) is located at a different side of a body midline or in a same side of the body midline.

7. A method according to any one of claims 4 to 6, wherein each of said at least two spaced apart ROIs is located above the waist line or below the waist line.

8. A method according to any one of claims 4 to 6, wherein at least one first ROI of said at least two spaced apart ROIs is located above the waist line, and at least one second ROI of said at least two spaced apart ROIs is located below the waist line.

9. A method according to claim 8, wherein said at least one first ROI comprises an arm region, and upper back region, a lower back region, and / or an abdomen region, and wherein said at least one second ROI comprises a leg region.

10. A method according to any one of the previous claims, wherein said positioning said at least 2 electrodes comprises positioning at least 3 electrodes above said tissue volume at said selected target ROI, and wherein said delivering comprises delivering said at least one electric field intermittently between at least two pairs of said at least 3 electrodes using at least one shared electrode of said at least 3 electrodes.

11. A method according to any one of the previous claims, wherein said generating comprises generating said at least one electric field with a frequency of at least 25Hz and with an intensity between 10mA and 80mA.

12. A method for delivery of an electric muscle stimulation training, comprising:selecting at least one target region of interest (ROI) in a subject body for said muscle stimulation training;positioning at least 3 electrodes on a surface of a tissue volume at said selected at least one target ROI;generating at least on electric field with parameter values suitable to contract at least one muscle in said tissue volume;79delivering said at least on electric field intermittently between at least 2 pairs of said at least 3 electrodes to said tissue volume, with timing values suitable for simultaneous contraction of at least 2 muscles in said tissue volume.

13. A method according to claim 12, wherein said positioning comprises positioning said at least 3 electrodes at a distance relative to each other suitable for generating contraction of muscles in at least two different directions by said at least one electric field, wherein an angle between said at least two directions is between 10 degrees and 180 degrees.

14. A method according to any one of claims 12 or 13, wherein said generating comprises generating said at least one electric field with a phase duration of between 50 ps and 500 ps, and with frequency between 1Hz and 150Hz.

15. A method according to any one of claims 12 or 13, comprising:generating said at least one electric field by at least one pulse generator electrically coupled to said at least 3 electrodes and positioned on said subject body.

16. A method according to claim 15, wherein said at least one electric field is generated with a frequency of at least 50 Hz, and wherein an electric field delivered between each pair of electrodes of said at least two pairs has a frequency of at least 25 Hz, and a pulse width between 100 ps and 1150 ps.

17. A method according to any one of claims 12 to 16, wherein said at least one electric field has an intensity between 10mA and 80mA.

18. A method according to any one of claims 12 to 17, wherein said delivering comprises delivering said at least one electric field intermittently between said at least two pairs of said at last 3 electrodes during a time period between 2 seconds and 60 minutes.

19. A method according to any one of claims 12 to 18, wherein said positioning said at least 3 electrodes comprises positioning at least 4 electrodes on said surface of said tissue volume at said selected at least one target ROI, and wherein said delivering said at least one electric field comprises delivering at least one first electric field intermittently between a first set of two electrode pairs of said at least 4 electrodes, and delivering at least one second electric80field intermittently between a second different set of two electrode pairs of said at least 4 electrodes having a shared electrode when said delivering of said at least one first electric field is stopped.

20. A method according to any one of claims 12 to 19, wherein said selected at least one target ROI comprises at least one of, a calf region of a leg, upper back, lower back and abdomen.

21. A method for delivery of a muscle stimulation training, comprising:selecting at least one target region of interest (ROI) in a subject body for said muscle stimulation training;positioning at least 3 electrodes on a surface of a tissue volume at said selected at least one target ROI;generating at least one electric field, with parameter values suitable to contract at least one muscle in said tissue volume;delivering said at least one electric field, between at least 2 pairs of said at least 3 electrodes to said tissue volume, with parameter values suitable for contraction of at least 2 different muscles in said tissue volume, wherein a duration of said delivering is between 2 minutes and 60 minutes, and wherein said delivering is performed while said at least 3 electrodes remain coupled directly or indirectly to said tissue surface during the delivering time.

22. A method according to claim 21, wherein said at least one target ROI comprises, at least one arm, at least one leg, an abdomen, buttocks, upper back, and / or lower back.

23. A method according to any one of claims 21 or 22, wherein said generating comprises generating said at least one electric field by at least one pulse generator electrically coupled to said at least 3 electrodes, and positioned on said subject body.

24. A method according to any one of claims 21 to 23, wherein said generating comprises generating said at least one electric field as a biphasic pulse having a plus phase and a minus phase, each with a phase duration of between 100 ps and 500 ps, and with frequency between 1Hz and 150Hz.8125. A method according to any one of claims 21 to 23, wherein said at least one electric field is generated with a frequency of at least 2 Hz, and wherein an electric field delivered between each pair of electrodes of said at least two pairs has a frequency of at least 1 Hz, and a pulse width between 100 ps and 1150 ps.

26. A method according to any one of claims 21 to 25, wherein said generating comprises generating said at least one electric field with an intensity between 10mA and 80mA.

27. A method according to any one of claims 21 to 26, wherein said selecting comprises selecting at least one first ROI and at least one second ROI, wherein said positioning comprising positioning at least 3 electrodes of at least one first stimulation module on a surface of a tissue volume at said at least one first ROI, and at least 3 electrodes of at least one second stimulation module on a surface of a tissue volume at said at least one second ROI;and wherein said delivering comprises delivering electric fields by said at least one first stimulation module and said at least one second stimulation module, in synchronization with timing parameters suitable for generating simultaneous or sequential contraction of muscles in said at least one first ROI and muscles in said at said at least one second ROI.

28. A method according to claim 27, wherein said at least one first ROI and said at least one second ROI are located at an upper body portion of a subject above a waist line, at a same side of the body midline or at opposite sides of the body midline.

29. A method according to claim 27, wherein said at least one first ROI and said at least one second ROI are located at a lower body portion of a subject below a waist line, at a same side of the body midline or at opposite sides of the body midline.

30. A method according to claim 27, wherein said at least one first ROI is located above the waist line and said at least one second ROI is located below the waist line.

31. A method according to claim 30, wherein said at least one first ROI comprises an abdomen region, and wherein said at least one second ROI comprises a leg region.

32. A stimulation module, comprising:82at least 3 electrodes configured to be coupled directly or indirectly to a skin surface of a subject at a distance from each other, and wherein said at least 3 electrodes are configured to deliver an electric field transcutanously to at least one tissue volume beneath said skin surface;a pulse generator configured to generate at least one electric field, wherein said pulse generator is electrically connected to each of said at least 3 electrodes;a memory circuitry configured to store electric field parameter values;a control circuitry, wherein said control circuitry signals said pulse generator to generate at least one electric field based on parameter values stored in said memory and to deliver said electric field sequentially or intermittently to at least 2 electrode pairs of said at least 3 electrodes with parameter values suitable for contracting simultaneously at least two muscles in said at least one tissue volume.

33. A stimulation module according to claim 32, wherein a frequency of a portion of said at least one electric field delivered between each pair of said at least 2 electrode pairs is between 25 Hz and 100 Hz.

34. A stimulation module according to any one of claims 32 or 33, wherein said at least one electric field is delivered with an intensity between 10 mA - 60 mA.

35. A stimulation module according to any one of claims 32 to 34, comprising at least one multiplexer module configured to direct the at least one electric field generated by the pulse generator to said at least 2 electrode pairs.

36. A stimulation module according to any one of claims 32 to 35, wherein said at least 3 electrodes are configured to be reversibly coupled to one or more electrode pads by magnetic coupling.

37. A stimulation module according to any one of claims 32 to 36, comprising a communication circuitry configured to communicate with at least one remote device.

38. A stimulation module according to claim 37, wherein said stimulation module is programmed based on signals received by the communication circuitry.8339. A stimulation module according to any one of claims 37 or 38, wherein said communication circuitry is configured to communicate with the at least one remote device using wireless signals.

40. A stimulation module according to any one of claims 32 to 39, comprising at least one battery, wherein said at least one battery is a rechargeable and / or a replaceable battery.

41. A stimulation module according to any one of claims 32 to 40, comprising at least one detector configured to detect signals indicating muscle fatigue, and wherein said control circuitry controls generation of said at least one electric field based on said detected signals received from said at least one detector.

42. A system for delivery of electrical muscle stimulation (EMS), comprising:at least one stimulation module, comprising:at least 3 electrodes, configured to be coupled to a tissue surface at a distance from each other;at least one pulse generator electrically connected to each of the at least 3 electrodes, configured to generate at least one electric field and to deliver the at least one electric field between at least 2 pairs of the at least 3 electrodes to at least one tissue volume underneath the tissue surface, wherein said electric field is generated with parameter values suitable to contract at least one muscle in said tissue volume;a control circuitry, wherein said control circuitry is configured to signal said at least one pulse generator to generate and deliver the at least one electric field in synchronization between the at least 2 pairs or electrodes;at least one battery electrically connected to said control circuitry;a communication circuitry;a control console, comprising:a memory circuitry storing at least one stimulation protocol or indications thereof;a communication circuitry configured to communicate with said at least one stimulation module;a control circuitry, wherein said control circuitry signals said at least one stimulation module to generate and deliver said at least one electric field, according to said at least one stimulation protocol or indications thereof stored in said memory.

43. A system according to claim 42, wherein said at least one stimulation module comprises at least two stimulation modules, in communication with said control console, and wherein said control console synchronizes activation of said at least two stimulation modules according to said at least one stimulation protocol, to deliver electric fields to at least 2 spacedapart tissue volumes, wherein parameter values of said electric fields are suitable to contract at least 2 muscles, each in a different tissue volume of said at least 2 spaced-apart tissue volumes .

44. A system according to any one of claims 42 or 43, wherein said control circuitry of said control console signals said at least one stimulation module to deliver said at least one electric field, during a time period between 10 minutes and 40 minutes while said at least one stimulation module remains coupled to said tissue surface.

45. A system according to any one of claims 42 to 44, wherein said control console comprises a user interface configured to generate a human detectable indication with information about an activation status of said at least one stimulation module.

46. A system according to claim 45, wherein said control console user interface generates said human detectable indication with information about an electrical power level in said at least one battery of said at least one stimulation module.

47. A system according to any one of claims 45 or 46, wherein said control console user interface is configured to receive at least one input signal with information about at least one of, electric field intensity, electric field frequency and timing values for delivery of an electric field by said at least one stimulation module, and wherein said control console is used for programming of said at least one stimulation module based on said at least one input signal.

48. A system according to any one of claims 42 to 47, wherein said at least one stimulation module comprise at least one position detector configured to detect a position of a stimulation module or a position of each of the at least 3 electrodes of the stimulation module.

49. A system according to any one of claims 42 to 48, comprising at least one detector for detecting signals indicating muscle fatigue, and wherein said control console is configured modify activation of said at least one stimulation module based on said detected signals.

50. A system according to any one of claims 42 to 49, wherein said at least one pulse generator generates said at least one electric field with a frequency between 25 Hz and 100 Hz, with intensity between 10 mA and 80 mA.

51. A system according to any one of claims 42 to 50, wherein said at least one pulse generator repeatedly generates said at least one electric field for a time period between 2 seconds and 12 second with intervals between 1 second and 10 seconds.

52. A system according to any one of claims 42 to 51, wherein said at least one stimulation module comprises electrical charging conductors, electrically coupled to the at least one battery, wherein said electrical charging conductors are configured to electrically couple said at least one battery to an external power source.

53. An electrode unit, comprising:a housing having a tissue contacting surface configured to be placed in contact directly or indirectly with a tissue surface;at least one electrode within said housing, wherein said electrode comprises an electric connector for connecting said electrode to an external power source;at least one magnetic connector configured to reversibly magnetically couple said at least one electrode to at least one electrical conductor of at least one electrode pad.

54. An electrode unit according to claim 53, wherein said at least one magnetic connector comprises at least one magnet configured to apply a magnetic field on at least a portion of said at least one electrical conductor.

55. An electrode unit according to any one of claims 53 or 54, wherein said at least one magnetic connector comprises at least two spaced apart magnetic connectors configured to reversibly couple said at least one electrode to said at least one electrical conductor of said at least one electrode pad.

56. An electrode pad, comprising:a body having a first surface and a second tissue contacting surface coated with an adhesive coating configured to attach said tissue contacting surface to a surface of a tissue:86at least two spaced apart electrical conductors crossing through said body between said second tissue contacting surface and said first surface, and extend through said first surface;wherein said at least two spaced apart electrical conductors are configured to conduct electricity through said electrode pad body to a tissue contacting the tissue contacting surface or said adhesive coating.

57. A charging module, comprising:a body comprising:a plurality of charging slots shaped as pockets arranged side by side in said body, wherein each charging slot is shaped and sized to receive electrodes of a stimulation module via an opening of the charging slot while keeping a control unit comprising a user interface and charging connectors of the stimulation module outside said charging slot;a plurality of pairs of charging connectors, wherein each pair of said charging connectors is positioned in said body above each opening, and is aligned with said opening;a base configured to allow placing of the charging module on a surface.

58. A charging module according to claim 57, comprising a plurality of magnetic connectors, each is adjacent to a pair of said charging connectors, wherein each of the plurality of magnetic connectors is configured to magnetically couple said control unit to said body while electrically coupling the control unit charging connectors to said pair of said charging connectors.

59. A charging module according to claim 57, wherein each pair of said charging connectors of said charging module comprises at least one magnetic connector configured to magnetically couple said control unit to said body while electrically coupling the control unit charging connectors to said pair of said charging connectors.

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