DEVICE AND METHOD FOR RECORDING THE MUSCLE ACTIVITY OF ONE OR MORE DEEP MUSCLES BY NON-INVASIVE MEASUREMENTS

Description

Technical field

[0001] The present application relates to a device and a method for directly and instantly measuring and quantifying the level of muscular activity of one or more deep muscles of the abdominal strap of a subject by non-invasive electromyographic measurements.

[0002] The area of ​​application concerns a variety of applications such as functional rehabilitation, sport, well-being, aesthetics or even functional diagnosis. State of the art

[0003] In the field of non-invasive measurement of muscle activity, we know of measurement by electromyography (EMG), which consists of positioning adhesive electrodes on the patient's skin, strategically in relation to the anatomy of the muscle for which we seek to record muscle activity.

[0004] This technique is limited because the signal collected can only be specific to the targeted muscle if the muscle is positioned just below the measuring electrode. It is therefore mainly applicable to so-called superficial muscles, located just below the skin. The SENIAM project (http: / / www.seniam.org / ) was also conducted with the aim of consolidating applied research in the field of surface electromyography, which resulted in the publication of European recommendations concerning sensors, their optimal positioning per targeted muscle and appropriate signal processing methods. These recommendations therefore concern 30 individual muscles, but do not include the deep muscles targeted by the present invention. At the same time, there have been several attempts to measure the muscle activity of deep muscles from surface EMG electrodes.

[0005] McGill et al (1996, J. Biomechanics, Vol 29, No 11, pp 1503-1507) investigated the possibility of measuring the muscle activity of 5 specific muscles (psoas, external oblique, internal oblique, transverse abdominis and quadratus lumborum) from a single surface EMG electrode strategically positioned for each muscle. This study shows that some surface anatomical sites could be used to reflect the muscle activity of deep muscles such as the quadratus lumborum and psoas. However, the measurement error is 6% to 12%. Furthermore, the findings show that the location that would allow measuring (with an error of 15%) the transverse abdominis is the same as the one that best represents the muscle activity of the internal oblique (15cm lateral to the navel, just above the inguinal ligament).Thus, this location is not specific to one of these two muscles and the method thus described does not make it possible to respond to the technical problem resolved by the present invention.

[0006] Jesinger and Stonick (1994, 6th IEEE DSP Workshop Proc., p57-60) propose to solve an inverse problem based on a finite element model of the electrical activity of deep muscles and its propagation to the skin surface. This method, like other methods based on similar principles of inverse resolution from a model, requires a large number of electrodes (more than 100) to obtain sufficient information to solve the mathematical problem. These methods are mainly used for research purposes and are not necessarily suitable for industrial applications for which calculations must be made in real time with a simple-to-use device.In the present invention, on the contrary, the device comprises a maximum of 5 measuring electrodes and allows the activity of each deep muscle of the abdominal belt, such as the transverse abdominal or the internal oblique, to be displayed in real time.

[0007] The invention described in US patent 9,687,168 consists of a method of surface electromyography of deep muscles. The invention consists of arranging a matrix of monopolar electrodes encircling the circumference of a part of the body in which is included the deep muscle that one seeks to investigate. The example of application chosen concerns the measurement of the brachialis muscle of the arm, by arranging two matrices of 6 electrodes each, configured in two concentric circles around the arm. Thus, if one seeks to apply the method to the case of the deep muscles of the abdominal strap, the number of electrodes in the matrix is ​​necessarily greater than 5, even for a person of small build.Furthermore, this patent does not teach the embodiment allowing the method to be applied to the deep muscles of the abdominal strap, given that a specific calibration phase of the distribution of the muscles of the investigated area is necessary for the application of the independent component analysis carried out subsequently.

[0008] Currently, there is no device or method for measuring the specific muscle activity of each deep muscle of the abdominal belt, based on non-invasive electromyographic measurements, by a non-circular arrangement of 1 to 5 surface EMG sensors placed on the skin of the moving subject.

[0009] An aim of the present application is to provide a device and a method allowing a user performing movements, to visualize and evaluate in real time the muscular activity of the different deep muscles of the abdominal strap (Transverse abdominal and Internal oblique).

[0010] Another aim of the present application is to provide a device for visualizing and evaluating in real time the muscular activity of the different deep muscles of the abdominal strap which is easily manipulated by the user. Description of the invention

[0011] For this purpose, the invention relates to a method according to claim 1.

[0012] For example, in the case of an implementation of the invention with 2 sensors, these can be placed on the skin of a subject according to the following indications: A sensor positioned in a band located below the line formed by the two anterior superior iliac spines, and above the pubic symphysis. This sensor can in this case be positioned between the two inguinal ligaments.

[0013] For example, in the case of an implementation of the invention with 3 sensors, these can be placed on the skin of a subject according to the following indications: Two sensors positioned symmetrically with respect to the subject's umbilicus / pubis axis, in a band located below the line formed by the two anterior superior iliac spines, and above the pubic symphysis. These two sensors can in this case be positioned between the two inguinal ligaments, and One sensor positioned on the Rectus Abdominis muscle.

[0014] For example, in the case of an implementation of the invention with 4 sensors, these can be placed on the skin of a subject according to the following indications: Two sensors positioned symmetrically with respect to the subject's umbilicus / pubis axis, in a band located below the line formed by the two anterior superior iliac spines, and above the pubic symphysis. These two sensors can in this case be positioned between the two inguinal ligaments, and Two sensors positioned on the Rectus Abdominis muscle.

[0015] For example, in the case of an implementation of the invention with 5 sensors, these can be placed on the skin of a subject according to the following indications: Two sensors positioned symmetrically with respect to the subject's umbilicus / pubis axis, in a band located below the line formed by the two anterior superior iliac spines, and above the pubic symphysis. These two sensors can in this case be positioned between the two inguinal ligaments, Two sensors positioned on the Rectus Abdominis muscle, and One sensor on the dorsal side, on a line connecting the anterior superior iliac spine and the L1-L2 intervertebral space, at the level of the L5 spinous process.

[0016] The sensors can be advantageously positioned to specifically measure the muscle activity of each targeted deep muscle. According to the invention, the sensors are positioned in a non-circular arrangement along the targeted muscle.

[0017] Advantageously, but optionally, the invention comprises at least one of the following characteristics: Means for viewing acquired, recorded, processed signals, or calculated indices. This may be, for example, any suitable means known to those skilled in the art, such as a computer monitor, a touchscreen tablet or a mobile phone screen. Means for recording signals at a sampling frequency between 500Hz and 3000Hz. This may be, for example, any suitable means known to those skilled in the art, such as, for example, a high-resolution analog / digital conversion acquisition chain combined with a memory. Means for applying signal processing algorithms selected from smoothing, thresholding, averaging, normalization, frequency analysis, temporal correlation analysis between at least two signals, or independent component analysis, or a combination of these methods. Wireless communication means for transmitting the acquired signals to the memory. This may be, for example, any suitable means known to those skilled in the art, such as, for example, the Bluetooth protocol, the Bluetooth Low Energy protocol, or the WIFI or LoRa protocol.Means for measuring the muscular activity of one or more deep muscles of the abdominal strap of a subject from bipolar EMG electrodes. This may be any suitable means known to those skilled in the art, such as for example a bipolar EMG, for example the 3M electrodes positioned on the muscle.

[0018] The invention relates to a method for measuring the muscle activity of the internal oblique and transverse abdominis of a subject using non-invasive surface electromyographic sensors.

[0019] The present application also relates to a device for measuring the specific muscular activity of one or more deep muscles of the abdominal strap of a subject from non-invasive surface electromyographic sensors comprising: Means for acquiring electrical signals from at least two sensors, the device being characterized in that the number of sensors is between 2 and 5. Means for recording the electrical signals acquired by the acquisition means in a memory. Means for processing the signals recorded by the recording means, making it possible to apply a combination of signal processing algorithms to the recorded signals to thereby deliver a plurality of processed signals. Means for calculating at least one index representative of the muscular activity of each of the at least one deep muscle of the abdominal strap of the subject and its temporal evolution. Means for visualizing the signals acquired, recorded, processed, or calculated indices.

[0020] For the purposes of the present application, the means for acquiring electrical signals, the means for recording electrical signals, the means for processing recorded signals, and the means for displaying signals may be any suitable means known to those skilled in the art, such as, for example, those mentioned above.

[0021] For the purposes of the present application, the calculation means may be any suitable means known to those skilled in the art, such as, for example, the execution of the algorithms within digital calculation environments or within a suitably programmed fast processor.

[0022] Advantageously, the method and the device make it possible to measure the muscular activity of several deep muscles (denoted N) simultaneously, while obtaining a specific, i.e. individualized, result for each muscle. In other words, the method and the device make it possible to carry out N measurements specific to each of the N targeted muscles, and to obtain the value of N muscular activities. Thus, it is possible to measure in a specific, i.e. individualized, manner the activity of either a single deep muscle, for example the transverse muscle, or of several deep muscles at the same time, for example the transverse muscle and the internal oblique, while being able to specifically attribute to each of the muscles the value of the muscular activity measured for this muscle.This result is completely different and advantageous compared to the methods and devices of the state of the art, which simply allow the muscular activity of a group of deep muscles to be measured, without knowing which muscle or muscles are involved in this result, or in what proportion.

[0023] The present application also relates to computer programs stored on an information medium, said programs comprising instructions making it possible to implement the methods described above, when they are loaded and executed by a computer system. Definitions

[0024] In the present application, the terms below are defined as follows: For the purposes of the present invention, the term "specific muscular activity of one or more muscles" means the individual muscular activity of each of the muscles for which the muscular activity measurement is carried out, whether the measurement is carried out on a single muscle, or on several muscles at the same time. The specific muscular activity is therefore an individualized value of the muscular activity specific to each of the muscles subjected to the measurement.

[0025] For the purposes of the present invention, the term "sensor" means any device for measuring the muscular activity of deep muscles. This may be, for example, any surface sensor such as surface electromyography (EMG) electrodes, of the unipolar and / or bipolar type, or an ultrasound probe, or needle EMG. For example, the number of sensors used in the electrical signal acquisition step may be 2, or 3, or 4, or 5. "Deep muscles" concerns the biological tissues composed of skeletal-type myocytes located under at least one other biological tissue composed of myocytes. "Abdominal strap" concerns the area delimited by the last ribs of a human subject and the pubic symphysis. Thus, within the meaning of the invention, the muscles of the abdominal strap therefore concern the skeletal muscles contained in this area, preferably but not limited to the muscles: Transverse Abdominal, Multifidus, Internal Oblique, Rectus Abdominis and External Oblique. "Draw-in" concerns an exercise for recruiting the transverse abdominal muscle consisting of asking the subject lying down, knees at 90° placed on a chair (or flexed with feet on the ground), to perform a slow and controlled maximum forced expiration by pulling in the stomach, then to hold this contraction for 5 seconds while inhaling only in the thoracic region."Blocked crunch" concerns an exercise for recruiting the abdominal muscles consisting of asking the subject lying on their back, knees at 90° on a support (or bent), arms behind the head, to try to raise their torso while an operator blocks the movement (via pressure on the shoulders) thus allowing the subject to raise their torso by approximately 30° in relation to the ground. Presentation of the drawings

[0026] Other characteristics, aims and advantages of the present application will appear on reading the following description of a non-limiting example of implementation, given with regard to the figures: There figure 1 is a representative diagram of a particular and non-limiting device for implementing the method of measuring the muscular activity of one or more deep muscles of the abdominal strap of a subject from non-invasive surface electromyographic sensors. figure 2is a schematic representation of a particular but non-limiting arrangement of 5 measuring electrodes allowing the implementation of the invention. figure 3 is a schematic representation of the muscular anatomy of the abdominal strap. figure 4 is a representation of EMG recordings made during preliminary tests, using the electrode arrangement described according to the figure 2 There Figure 5 is a representation of the temporal evolution of a muscular activity index for the transverse abdominal muscle obtained by applying the method on two separate individuals during the execution of repeated “Draw-In” maneuvers. figure 6 is a schematic representation of a particular but non-limiting arrangement of 5 measuring electrodes allowing the implementation of the invention. The figure 7is a schematic representation of a particular but non-limiting arrangement of 3 measuring electrodes allowing the implementation of the invention. The figure 8 is a schematic representation of a generalized arrangement of the measuring electrodes in a strip located below the line formed by the two anterior superior iliac spines and above the pubic symphysis allowing the implementation of the invention. Detailed description Example of realization

[0027] In reference to the figure 1 , the device allows the implementation of a method for measuring the muscular activity of one or more deep muscles of the abdominal strap of a subject from surface electromyographic sensors 10 non-invasive including: One step I acquisition of electrical signals from at least two sensors 10, the method being characterized by the fact that the number of sensors is between 2 and 5, One step II recording of electrical signals acquired during the step I in a memory 41, One step III processing of signals recorded at the stage II based on the application on the signals recorded at the stage II of a combination of signal processing algorithms in a signal processing module 42 and thus delivering a plurality of processed signals (s 1 (t), s 2 (t), s 3 t)...sn (t)), One step IV calculation of at least one index representative of the muscular activity of at least one deep muscle of the abdominal strap of the subject and its temporal evolution in an index calculation module 43.

[0028] In the example described, representative but not limiting, the device comprises 5 surface EMG measuring electrodes 11, 12, 13, 14 and 15. In the example described these are bipolar electrodes (system Wireless Miniwave Infinity ) .The simultaneous acquisition of the 5 sensors is synchronized thanks to the triggering of a trigger 30. Each measuring electrode is connected to a pre-treatment unit 20. This unit 20 then includes an electrode acquisition chain 21, 22, 23, 24 and 25. Each processing chain contains an amplification module, a filtering module and an analog-digital conversion module. The figure only shows the acquisition chain in detail. 21 of the electrode 11, therefore including the amplification module 211, the filtering module 212 as well as an analog-to-digital conversion module 213. In the example described, the filters applied to the signals are those conventionally used for the acquisition of EMG signals and known to those skilled in the art. The analog-digital conversion was carried out at 2kHz on 16 bits.

[0029] The pretreatment unit 20contains communication means for transferring the data thus acquired during step I to a processor 40.

[0030] Advantageously, but optionally, these means of communication can implement wireless communication protocols.

[0031] The processor 40 contains a memory 41 in which the acquired signals will be stored during data recording step II.

[0032] This memory also calls various signal processing algorithms used by the signal processing module 42 to carry out stage III of signal processing. The application of these signal processing algorithms will lead to the calculation of processed signals (sit), i being between 1 and 10, then to the calculation of indices representative of the muscular activity of the deep muscles of the abdominal strap via an index calculation module 43.

[0033] These indices, as well as their temporal evolutions, can then be viewed on a monitor 50. This monitor 50 also allows to visualize in real time the signals acquired during the acquisition step I, or to visualize them once recorded in the memory after the recording step II, or to visualize the signals si (t) generated during the signal processing step III.

[0034] In reference to the figure 2 , a particular and non-limiting implementation of the invention may consist of positioning 5 EMG measuring electrodes on the surface of the skin of a subject 201 according to the following anatomical sites: An electrode 11 3 cm lateral to the navel An electrode 12 15 cm lateral to the navel An electrode 13 positioned under the electrode 12, just above the inguinal ligament An electrode 14placed symmetrically to the electrode 13 An electrode 15 on the dorsal side, on a line connecting the anterior superior iliac spine and the L1-L2 intervertebral space, at the level of the L5 spinous process.

[0035] The described implementation of the invention will be identical for: an electrode 11 placed between 1 cm and 5 cm lateral to the navel, to the left or to the right of the subject 201. an electrode 12 placed between 10 cm and 25 cm lateral to the navel, to the left or to the right of the subject 201 an electrode 13 positioned under the electrode 12, at a distance of between 4 cm and 15 cm, without exceeding the subject's inguinal ligament 201

[0036] There figure 3schematically represents different muscles of the abdominal strap, composed of 4 pairs of muscles, which are organized symmetrically on either side of the abdomen on three distinct layers. We therefore find among these abdominal muscles the following pairs: Note GD in the figure: The Rectus Abdominis (the right rectus abdominis and the left rectus abdominis). Constituting the anterior wall of the abdomen, the Rectus Abdominis muscle descends from the thorax to the pubis in the form of a long flat muscle. Noted OE in the figure: The external oblique, attached to the last 7 ribs, which extends from the center of the abdomen to the latissimus dorsi, thus occupying a good part of the sides of the abdomen. Noted OI in the figure: The internal oblique, which inserts on the entire anterior part of the iliac crest (like the transverse, but more on the surface) Noted TrAin the figure: The transverse, a broad muscle, the deepest of the abdominal muscles. Located in the lateral part of the abdomen, the transverse muscle is horizontal, and thus passes behind the Rectus Abdominis muscle.

[0037] Thanks to these elements, the device allows the electrical signals from each surface EMG measuring electrode to be measured in real time. 11, 12, 13, 14 and 15, each electrode thus measuring a combination of all the contributions from the muscular activities of the different muscles being close to said electrode.

[0038] The objective of the method is to calculate indices representative of the muscular activity of the deep muscles of the abdominal belt.

[0039] In the example detailed here, the device will calculate 3 indices: i 1: internal oblique contraction index OI, equal to 1 if the internal oblique muscle is contracted, 0 otherwise i 2: contraction index of the transverse abdominal muscle TrA equal to 1 if the transverse abdominal muscle is contracted, 0 otherwise i 3: index of the contraction force of the transverse abdominal muscle TrA, proportional to the contraction force of the transverse abdominal muscle, and expressed as a percentage of the MCV for this muscle (Maximum Contraction Value)

[0040] These indices and their temporal evolutions will be calculated over the same sampling period as the acquisition.

[0041] During step III of signal processing, the first step, representative of the invention but not limiting, consists of applying a combination of different processing algorithms in order to clean the recorded signals. Each electrode leads to a recorded signal noted EMG(1 i ) for i ranging from 1 to 5 according to the non-limiting example described.

[0042] Each EMG signal(1 i ) was therefore processed as follows: Rectification: this involves, after evaluating the baseline, then correcting the EMG signal(1 i ) by this offset, retaining only the absolute value of the signal to recover a strictly positive signal. Normalization with respect to maximum values ​​measured on recordings obtained when the subject performs specific exercises which lead to near-maximal contractions of the different muscles of the subject's abdominal strap, to the extent of the subject's capacity. To obtain these maximum values, the method consists of using the device to record the signals from the electrodes while the subject performs a "Draw-In" maneuver or a "Blocked Crunch" maneuver, for example. Smoothing over a 1ms time window: this involves calculating the time average over a 1ms sliding window. The method can be implemented with a sliding window size between 0.5ms and 100ms.

[0043] These steps therefore lead to modified EMG(1i) signals, subsequently noted EMG'(1i).

[0044] In the example described, representative but not limiting of the invention, it is assumed that the signals of the surface electrodes are a combination of the contributions of the 4 muscles of the abdominal strap described on the figure 3 , namely the great law ( GD ), the external oblique ( OE ), the internal oblique ( OI ) and the transverse abdominal ( TrA ). The electrical activity of each of these muscles can be represented by the expressions A GD , A OE , A OI and A TrA , each electrode therefore receiving a weighted sum of these activities at each instant (equation given for the electrode 11 ): EMG 11 = α 11 . A GD + β 11 . A OE + γ 11 . A OI + δ 11 . A TrA

[0045] This is therefore a system of 5 equations with 20 parameters and 4 unknowns, based on 5 recordings of 4 muscular activities which will be considered as statistically independent. The mathematical method therefore consists of determining the values ​​of the 20 weighting coefficients in order to be able, by subsequently inverting the system, to isolate either the electrical activity A OI allowing the calculation of the index i 1 , or the electrical activity A TrA , allowing the calculation of the indices i 2 and i 3 .

[0046] This was done by source separation analysis, implemented in the matrix calculation software Scilab (registered trademark).

[0047] The index i 1 is then calculated as being equal to 1 if the amplitude of the signal A OI is greater than a threshold set between 5% and 15% of its maximum value, 0 otherwise.

[0048] The index i 3 is then calculated as being equal to 1 if the amplitude of the signal A TrA is greater than a threshold set between 5% and 15% of its maximum value, 0 otherwise.

[0049] The index i 2 is then calculated as a percentage of the value of the signal A TrA .

[0050] The device thus makes it possible to visualize in real time the evolution of the value of the indices when the subject performs movements, or muscle strengthening exercises or even rehabilitation exercises.

[0051] There Figure 5 thus illustrates the representation of the contraction index of the transverse abdominal muscle i 2 while the subject performs repeated Draw-In maneuvers, interspersed with 10 s rest periods.

[0052] The device also allows the activity of the transverse abdominal muscle to be displayed in real time in several modes: "on / off" (representing the index i 2 ), or a visualization of the contraction intensity as a function of time (index i 3 ), which can be superimposed on an "ideal" instruction which must be followed by the subject, thus consciously controlling the contraction of his muscles.

[0053] In reference to the figure 6 , a particular and non-limiting implementation of the invention may consist of positioning 5 EMG measuring electrodes on the surface of the skin of a subject 201 according to the following anatomical sites: An electrode 11 3 cm lateral to the navel An electrode 12 15 cm lateral to the navel, then up to the 8th rib. An electrode 13 positioned 2cm to the left of the electrode 12 , towards the center of the subject An electrode 14positioned 15cm to the right of the subject's navel, then going back down to the inguinal ligament. An electrode 15 on the dorsal side, on a line connecting the anterior superior iliac spine and the L1-L2 intervertebral space, at the level of the L5 spinous process.

[0054] The described implementation of the invention will be identical for: an electrode 11 placed between 1 cm and 5 cm lateral to the navel, to the left or to the right of the subject 201. an electrode 12 placed between 10 cm and 25 cm lateral to the navel, to the left or to the right of the subject 201 an electrode 13 positioned between 1cm and 5cm lateral to the electrode 12, towards the center of the subject

[0055] In another embodiment, regarding a device comprising 5 electrodes positioned again as shown in figure 2 or as shown in the figure 6, the signals recorded by the surface EMG measuring electrodes 13 And 14 can also be analyzed by a measurement of the temporal correlation function in order to then condition the calculation of the indices I 1 and I 2 .

[0056] The index i 1 will be equal to 1 if the amplitude of the signal A OI is greater than a threshold set between 5% and 15% of its maximum value AND if the two signals EMG' (13) and EMG' (14) are weakly correlated, 0 otherwise. The index i 3 is then calculated as being equal to 1 if the amplitude of the signal A TrA is greater than a threshold set between 5% and 15% of its maximum value AND if the two signals EMG' (13) and EMG' (14) are highly correlated, 0 otherwise.

[0057] In another non-limiting embodiment, relating to a device comprising 5 electrodes positioned again as shown in figure 2 , or the figure 6 , or comprising 3 electrodes as described in figure 7 , the EMG'(1i) signals are analyzed by applying a frequency analysis to condition the calculation of the indices i 1 and i 3 . The Fourier transforms of the EMG'(1i) signals are calculated to represent the frequency spectra. We then identify a frequency band characteristic of the deep muscle that we seek to characterize, or a ratio of characteristic frequency bands to thus condition the calculations of the indices I 1 and I 2 .

[0058] For example, if X i (f) are the respective Fourier transforms of the EMG'(1i) signals, and DSP i the power spectral densities of these Fourier transforms, calculated over a suitable integration time.

[0059] The following calculation is then carried out on each measurement channel: Ri = ∫ f 1 f 2 DSPi ∫ 0 fmax DSPi

[0060] Where f 1 and f 2 are two cut-off frequencies, f 1 is between 0 and 100Hz, and f 2 is between 50 and 200Hz. The values ​​chosen for these two cut-off frequencies vary from one electrode to another.

[0061] For example, for electrodes 11, 14 and 13, the embodiment can be implemented by choosing f 1 = 65Hz and f 2 = 95Hz.

[0062] The index i 1 is then calculated as being equal to 1 if the following conditions are commonly met: R 14 and R 13 are simultaneously greater than a threshold set between 0.55 and 0.8. R 11 is less than a threshold between 0.1 and 0.35.

[0063] Otherwise, i 1 is 0.

[0064] A particular and non-limiting implementation may consist of positioning 3 EMG measuring electrodes on the surface of a subject's skin according to the following anatomical sites: An electrode 11 3 cm lateral to the navel An electrode13 positioned 2 cm lateral to the anterior superior iliac spine towards the navel, then 2 cm longitudinally towards the feet. An electrode 14 placed symmetrically to the electrode 13.

[0065] The embodiments described above are specific and not limiting.

Claims

1. A method of measuring the simultaneous individual muscle activity of the internal oblique and transverse abdominis, and optionally one or more additional deep muscles of the abdominal belt chosen from the multifidus, the rectus abdominis and the external oblique, of a subject performing muscle strengthening exercises for aesthetic or sporting purposes using non-invasive surface electromyographic sensors (10) positioned in a non-circular arrangement along the targeted muscle comprising, for each deep muscle, the following steps (I) to (IV) a. A step (I) of acquisition of electrical signals from at least two sensors (10), the method being characterised by the fact that the number of sensors is between 2 and 5, b. A step (II) for recording the electrical signals acquired during step (I) in a memory (41), c. A step (III) of processing the signals recorded in step (II) based on the application to the signals recorded in step (II) of a combination of signal processing algorithms in a signal processing module (42) comprising rectification, normalisation, smoothing, thresholding, and source separation analysis, and thus delivering a plurality of processed signals (s1(t), s2(t), s3(t)....sn(t)), d. A step (IV) of calculating an index from the signals obtained in step c., representative of the individual muscular activity of each of at least one deep muscle of the subject's abdominal belt, by means of the execution of algorithms within digital computing environments or within a processor, and its temporal evolution in an index calculation module (43).

2. Method according to claim 1, comprising a step of visualisation of the acquired, recorded and processed signals or of the calculated indices.

3. Method according to one of claims 1 or 2, in which the step (I) recordings are made at a sampling frequency between 500Hz and 3000Hz.

4. Method according to any one of claims 1 to 3, in which the sensors (10) are bipolar EMG electrodes.

5. Method according to any one of claims 1 to 4, in which the communication of the signals acquired during step (I) to memory (41) is implemented by a wireless data communication process.