Oral muscle training instrument and oral muscle training method

Abstract

Provided are an oral muscle training instrument and an oral muscle training method, whereby it becomes possible to effectively stimulate a genioglossus muscle that is a deep muscle in the oral cavity. The oral muscle training instrument is provided with: a pair of electrodes that are arranged in the oral cavity; an electrode that is branched from one of the pair of electrodes and is arranged on the surface of the skin; and an electric circuit that distributes a medium frequency current between the electrodes. The pair of electrodes are placed on the tongue, and the electrode arranged on the surface of the skin is placed below the chin or in the front of the neck. It is possible that the pair of electrodes is placed on the tongue and the electrode arranged on the surface of the skin is placed on approximately the entire circumference of the neck. The medium frequency current is such a burst wave current that a procedure including continuously distributing a continuous wave current of 3 kHz or more and less than 8 kHz or a current of 3 kHz or more and less than 8 kHz for a predetermined time and subsequently halting the distribution of the current for a predetermined time is repeated.

Description

Oral muscle training device and oral muscle training method

[0001] The present invention relates to a technique for training oral muscles, particularly tongue muscles such as the genioglossus, for the purpose of treating or preventing sleep apnea syndrome (SAS) and swallowing disorders.

[0002] In sleep apnea syndrome, particularly obstructive sleep apnea syndrome (OSAS), fatty tissue accumulates in the pharynx, narrowing the airway and increasing inhalation flow rate. This is because, while the human skeleton generally stops growing significantly after the age of 20, muscle and fat mass continue to increase after the age of 20, resulting in a narrowing of the airway. Furthermore, with age and certain illnesses, pharyngeal tonus (tongue autonomy during sleep) declines, causing the tongue to be sucked into the trachea during inspiration, obstructing the airway and resulting in apnea. As a result, while normal individuals sleep with their mouths closed and their tongues elevated, patients with sleep apnea experience an open, tongue-down position. To improve tongue autonomy in these conditions, electrical stimulation of the genioglossus and other tongue muscles, as well as nerve stimulation to restore pharyngeal tonus, are considered effective treatments. Oral muscle training is also effective in treating or preventing swallowing disorders.

[0003] As a device for training tongue muscles such as the genioglossus using electrical stimulation, an oral muscle training device is known in which electrodes are placed inside or outside the oral cavity and an electric current is applied to the electrodes (see Patent Document 1). The oral muscle training device of Patent Document 1 includes multiple electrode means and an electric circuit, and applies an electric current to the electrode means to provide electrical stimulation to the oral muscles, thereby increasing the tension of the oral muscles and training the tongue muscles. However, the oral muscle training device of Patent Document 1 has a problem in that the two electrodes placed outside the oral cavity are positioned laterally from the midline of the user's face, making it difficult to effectively stimulate only the targeted deep muscles in the oral cavity (tongue muscles such as the genioglossus).

[0004] Special Publication No. 2022-505209

[0005] As described above, training the tongue muscles using electrical stimulation is effective for treating or preventing sleep apnea syndrome, but conventional devices have been unable to sufficiently electrically stimulate the genioglossus, the largest of the tongue muscles. In view of this situation, an object of the present invention is to provide an oral muscle training device and oral muscle training method that can effectively stimulate the genioglossus, a deep muscle in the oral cavity.

[0006] To solve the above problems, the oral muscle training device of a first aspect of the present invention includes a pair of electrodes placed in the oral cavity, an electrode branched from one of the pair of electrodes and placed on the skin surface, and an electrical circuit for passing a medium-frequency current between the electrodes. By placing a pair of positive and negative electrodes in the oral cavity in the case of direct current, or a pair of electrodes in the case of alternating current, with one of the electrodes branched and placed as a skin electrode, the deep muscles in the oral cavity can be effectively stimulated. Note that the term "skin surface" here does not refer to the entire surface of human skin, but rather refers to the skin surface below the tongue and above the heart. The purpose of limiting the area above the heart is to prevent electrical current from flowing to the heart, which could cause arrhythmia.

[0007] In the oral muscle training device of the first aspect of the present invention, it is preferable that the pair of electrodes be positioned on the tongue, and the electrode positioned on the skin surface be positioned under the chin or on the front of the neck. By positioning the pair of electrodes on the tongue and the electrode on the skin surface under the chin or on the front of the neck, when a current is applied to the electrodes, the current flows vertically along the midline of the person, thereby more effectively stimulating the deep muscles in the oral cavity. Furthermore, in the oral muscle training device of the first aspect of the present invention, the pair of electrodes may be positioned on the tongue, and the electrode positioned on the skin surface may be positioned approximately around the entire neck. By positioning the electrodes positioned on the skin surface approximately around the entire neck, the nerves and muscles of the genioglossus muscle can be effectively stimulated. Furthermore, the current density of the electrode positioned on the skin surface can be reduced, preventing obstruction of blood flow in the carotid artery.

[0008] In the oral muscle training device according to the first aspect of the present invention, the pair of electrodes may be arranged at the tip and the back of the tongue. "Arranged at the tip and the back of the tongue" here defines the relative positional relationship between the pair of electrodes and does not, for example, limit the distance between the electrodes. Furthermore, the electrode having the same potential as the electrode arranged on the skin surface may be the electrode at the tip of the tongue or the electrode at the back of the tongue.

[0009] In the oral muscle training device of the first aspect of the present invention, the pair of electrodes may be arranged on the left or right side of the midline, and the electrode arranged on the skin surface may be arranged on the opposite side of the midline from the pair of electrodes. Furthermore, in the oral muscle training device of the first aspect of the present invention, the pair of electrodes may be arranged point-symmetrically with respect to a point on the center line of the tongue between the tip and the back of the tongue. Because the tongue is prone to sudden movements, the terms center line and midline are used interchangeably. However, when the tongue is stationary and not moving left or right, the center line and midline are synonymous. Furthermore, in the oral muscle training device of the first aspect of the present invention, the electrodes arranged on the skin surface may be branched into at least two, and in the case of an even number of electrodes, they may be arranged line-symmetrically with respect to the midline. In the case of an odd number of electrodes, one electrode may be arranged on the midline and the other electrode may be arranged line-symmetrically with respect to the midline.

[0010] In the oral muscle training device of the first aspect of the present invention, the pair of electrodes may be three electrodes arranged at the tip, middle and back of the tongue, and one pair may be formed by an electrode in the middle of the tongue and an electrode at the tip and back of the tongue. In the oral muscle training device of the first aspect of the present invention, the pair of electrodes may be a plurality of pairs of electrodes, and adjacent electrodes have opposite polarities.

[0011] In the oral muscle training device of the first aspect of the present invention, the medium-frequency current is a continuous wave current of 3 kHz or more and less than 8 kHz. Alternatively, it may be an intermittent wave in which a current of 3 kHz or more and less than 8 kHz flows continuously for a predetermined time, followed by a period of no current for a predetermined time (e.g., one second or more), or the current of 3 kHz or more and less than 8 kHz may be a low-frequency intermittent wave current of 1 to 100 Hz (also referred to in this specification as a burst wave current). Furthermore, a combination of a continuous wave current and a burst wave current may be used. The medium-frequency current is more preferably 3 kHz or more and less than 5 kHz.

[0012] An oral muscle training device according to a second aspect of the present invention comprises: a first pair of electrodes arranged in the oral cavity; a first surface electrode branched from one of the first pair of electrodes and arranged on the skin surface; an electric circuit for passing a first medium-frequency current between the electrodes consisting of the first pair of electrodes and the first surface electrode; and an electric circuit for passing a second medium-frequency current between the electrodes consisting of the second pair of electrodes and the second surface electrode, a second pair of electrodes branched from one of the second pair of electrodes and arranged on the skin surface. In the oral muscle training device according to the second aspect of the present invention, it is preferable that the first and second pairs of electrodes are arranged on the tongue, and the first and second surface electrodes are arranged under the chin or on the front of the neck.

[0013] The electrode set of the present invention is a set of an electrode placed in the oral cavity and an electrode placed on the skin surface in any of the oral muscle training devices described above.

[0014] The oral muscle training method according to a first aspect of the present invention comprises the following steps 1) to 3): 1) placing a pair of electrodes on the tongue in the oral cavity, 2) placing an electrode branched from one of the pair of electrodes on the skin surface under the chin or on the front of the neck, and 3) passing a medium-frequency current between the electrodes.

[0015] In the oral muscle training method of the first aspect of the present invention, the step of arranging the pair of electrodes may comprise arranging the pair of electrodes at the tip and the back of the tongue. In the oral muscle training method of the first aspect of the present invention, the step of arranging the pair of electrodes may comprise arranging the pair of electrodes to the left or right of the midline, and the step of arranging the pair of electrodes on the skin surface may comprise arranging an electrode branching from one of the electrodes on the opposite side of the midline to the pair of electrodes. In the oral muscle training method of the first aspect of the present invention, the step of arranging the pair of electrodes may comprise arranging the pair of electrodes point-symmetrically with respect to a point on the center line of the tongue between the tip and the back of the tongue.

[0016] In the oral muscle training method of the first aspect of the present invention, the step of placing electrodes on the skin surface may include branching at least two electrodes branching from one electrode, and arranging the electrodes line-symmetrically with respect to the midline if the number of branched electrodes is even, or arranging one electrode on the midline and the other electrode line-symmetrically with respect to the midline if the number of branched electrodes is odd. In the oral muscle training method of the first aspect of the present invention, the pair of electrodes may be three electrodes arranged at the tip, middle, and back of the tongue, and each pair may consist of an electrode in the middle of the tongue and an electrode at the tip and back of the tongue. The oral muscle training method of the first aspect of the present invention may also include the following steps 1) to 3): 1) placing a pair of electrodes on the tongue in the oral cavity; 2) placing electrodes branching from one of the pair of electrodes on the skin surface around substantially the entire circumference of the neck; and 3) passing a medium-frequency current between the electrodes.

[0017] An oral muscle training method according to a second aspect of the present invention comprises the following steps A) to E): A) placing a first pair of electrodes on the tongue in the oral cavity; B) placing a second pair of electrodes on the tongue in the oral cavity; C) placing a first surface electrode branched from one of the first pair of electrodes on the skin surface under the chin or on the front of the neck; D) placing a second surface electrode branched from one of the second pair of electrodes on the skin surface under the chin or on the front of the neck; and E) passing a first medium-frequency current between the electrodes formed by the first pair of electrodes and the first surface electrode, and a second medium-frequency current between the electrodes formed by the second pair of electrodes and the second surface electrode.

[0018] The oral muscle training device and oral muscle training method of the present invention have the effect of effectively stimulating the genioglossus muscle, which is a deep muscle in the oral cavity, and also have the effect of stimulating the muscles required for swallowing.

[0019] FIG. 1 is a functional block diagram of the oral muscle training device of Example 1. FIG. 1 is a structural image of the oral muscle training device of Example 1. FIG. 2 is a usage image of the oral muscle training device of Example 1. FIG. 3 is an electrode arrangement image of Example 1. FIG. 4 is an electrode arrangement image of Example 5. FIG. 6 is an electrode arrangement image of Example 7. FIG. 8 is an electrode arrangement image of Example 9. FIG. 10 is an electrode arrangement image of Example 11. FIG. 1 is a functional block diagram of the oral muscle training device of Example 11. FIG. 1 is a structural image of the oral muscle training device of Example 11. FIG. 1 is an electrode arrangement image of Example 12. (1) FIG. 12 is an electrode arrangement image of Example 12. (2) Schematic flow diagram of the oral muscle training method of Example 1. FIG. 1 is a functional block diagram of the oral muscle training device of Example 12. FIG. 1 is a structural image of the oral muscle training device of Example 12. (3) FIG. 1 is a structural image of the oral muscle training device of Example 12. (4) Schematic flow diagram of the oral muscle training method of Example 12. FIG. 13 is an electrode arrangement image of Example 13.

[0020] An example of an embodiment of the present invention will be described in detail below with reference to the drawings. Note that the scope of the present invention is not limited to the following examples and illustrated examples, and many modifications and variations are possible.

[0021] Fig. 1 shows a functional block diagram of one embodiment of the oral muscle training device of the present invention. As shown in Fig. 1, the oral muscle training device 1 comprises an intraoral stimulation device 2, a skin surface stimulation device 3, and a stimulation current generator 4. The intraoral stimulation device 2 includes a pair of electrodes disposed in the oral cavity, namely, a first intraoral stimulation electrode 21 and a second intraoral stimulation electrode 22. The stimulation current generator 4 is connected to the first intraoral stimulation electrode 21 by a lead wire 5a and to the second intraoral stimulation electrode 22 by a lead wire 5b.

[0022] The skin surface stimulation device 3 includes a skin stimulation electrode 30 and a fixing band 6. The fixing band 6 is provided with the skin stimulation electrode 30. The skin stimulation electrode 30 is an electrode that branches off from the second intraoral stimulation electrode 22, which is one of a pair of electrodes placed in the oral cavity, and is placed on the skin surface, and is connected to the stimulation current generator 4 via a lead wire 5c that is connected to a lead wire 5b. The second intraoral stimulation electrode 22 and the skin stimulation electrode 30 have the same potential, and the second intraoral stimulation electrode 22 and the skin stimulation electrode 30 have different potentials from the first intraoral stimulation electrode 21. The stimulation current generator 4 is a device that can apply a medium-frequency current, and the medium-frequency current is applied by operating operation buttons (4a, 4b) for turning the current on / off and for adjusting the medium-frequency frequency. A medium-frequency current is an alternating current with a frequency of 1 kHz to 10 kHz, but in this embodiment, a continuous wave current (alternating current) of 3 kHz to 8 kHz is used. Subjective experiments showed that frequencies below 3 kHz felt too strong, while frequencies above 8 kHz were difficult to feel. Operation details are displayed on the display unit 4c. The stimulation current generator 4 and lead wires (5a to 5c) form an electrical circuit that passes a medium-frequency current between the electrodes.

[0023] Fig. 2 shows a schematic diagram of the oral muscle training device. As shown in Fig. 2, in the oral stimulation device 2, a first oral stimulation electrode 21 and a second oral stimulation electrode 22 are provided on a base 23. The fixing band 6 is worn so as to cover the back of the head and chin of a person, and a skin stimulation electrode 30 is provided on the inner surface.

[0024] Fig. 3 shows an image of how the oral muscle training device is used. As shown in Fig. 3, a user 7 wears a fixing band 6 to which a skin stimulation electrode 30 is attached on the head, and then holds the oral stimulation device 2 shown in Fig. 2 in the mouth. When the user 7 wears the fixing band 6, the skin stimulation electrode 30 is arranged so as to extend left and right from a position where it contacts the thyroid cartilage. By fixing the skin stimulation electrode 30 to the fixing band 6, the user 7 can position and fix the skin stimulation electrode 30 in an appropriate position simply by wearing the fixing band 6, improving the training effect and convenience.

[0025] FIG. 4 shows an illustration of the electrode arrangement in this embodiment. For ease of explanation, FIGS. 4, 6-14, 17, 18, and 23-26 only show the electrode arrangement in the device, and the electrode shapes are also exaggerated. As shown in FIG. 4, in the oral muscle training device 1, the first intraoral stimulating electrode 21 and the second intraoral stimulating electrode 22 are arranged on the tongue 7a of the user 7 along the midline 7c, which is a line that runs vertically straight through the center of the front of a human or animal. The first intraoral stimulating electrode 21 is arranged at the back of the tongue, i.e., toward the throat, and the second intraoral stimulating electrode 22 is arranged at the tip of the tongue, i.e., toward the mouth. Furthermore, the cutaneous stimulating electrode 30 is arranged on the skin of the neck 7b of the user 7, extending left and right from the midline 7c. By making the cutaneous stimulating electrode 30 wider or longer, it is possible to pass a medium-frequency current through a wider area for stimulation. Furthermore, by using the skin stimulation electrode 30, the skin stimulation electrode can be configured with one electrode, allowing for simple specifications.

[0026] FIG. 5 is a diagram illustrating the functions of the oral muscle training device. As shown in FIG. 5, a positive or negative electrode is placed on the tongue 7a of a user 7, and an electrode branching from one electrode is placed at the neck, where oral muscles such as the tongue and genioglossus muscles are sandwiched. As shown in current flow diagram 8, oral muscles such as the tongue and genioglossus muscles 70 are stimulated by current flowing through the first intraoral stimulating electrode 21, the second intraoral stimulating electrode 22, and the cutaneous stimulating electrode 30. Table 1 below shows the voltage, current, and resistance values ​​of the intraoral or cutaneous stimulating electrodes when current of each frequency is applied. The applied current is a continuous wave of 4 kHz to 8 kHz.

[0027]

[0028] As shown in Table 1, the current values ​​flowing through the intraoral electrodes were 3.4 mA at 4000 Hz, 2.5 mA at 6000 Hz, and 2.7 mA at 8000 Hz. In contrast, the current values ​​flowing through the electrodes on the neck skin were 10.8 mA at 4000 Hz, 13.0 mA at 6000 Hz, and 13.4 mA at 8000 Hz, indicating that the current flowing through the cutaneous stimulation electrode was greater. While the cutaneous stimulation electrode 30 is placed on the front of the neck 7b, the cutaneous stimulation electrode 31, shown by the dashed line, may alternatively be placed at a position below the chin 7d. The cutaneous stimulation electrodes 30 and 31 may have the same shape, or may have different shapes to accommodate the human body shape. Furthermore, the cutaneous stimulation electrodes 30 and 31 may be used together. By adopting such an electrode arrangement, it is possible to improve the current density in the area from the tongue to the submandibular region or between the tongue and the neck, thereby effectively stimulating oral muscles such as the tongue and genioglossus muscles. In all of Examples 2 to 12 described below, examples are shown in which one of the skin stimulation electrodes (30, 30a to 30e) is placed on the front of the neck 7b, but an electrode may also be placed at the submandibular region 7d, as with the skin stimulation electrode 31. Furthermore, although not shown in Examples 2 to 10, the configuration in which a current is applied via lead wires using a stimulation current generator 4 is the same as in this example.

[0029] Fig. 19 shows a schematic flow diagram of the oral muscle training method of this embodiment. As shown in Fig. 19, first, a pair of electrodes is placed on the tongue in the oral cavity (step S01). Next, an electrode branched from one of the pair of electrodes is placed on the skin surface of the front of the neck (step S02). After this placement, a medium-frequency current is applied between the electrodes (step S03). Note that the order of steps S01 and S02 may be reversed.

[0030] Fig. 6 shows an image of electrode arrangement in another embodiment. As shown in Fig. 6, in the oral muscle training device 1a, a first intraoral stimulating electrode 21 and a second intraoral stimulating electrode 22 are arranged along the midline 7c on the tongue 7a of the user 7, with the first intraoral stimulating electrode 21 at the tip of the tongue and the second intraoral stimulating electrode 22 at the back of the tongue. Furthermore, a cutaneous stimulating electrode 30 is arranged on the skin of the neck 7b of the user 7, extending left and right around the midline 7c. The first intraoral stimulating electrode 21 and the cutaneous stimulating electrode 30 are at opposite potentials, and the second intraoral stimulating electrode 22 and the cutaneous stimulating electrode 30 are at the same potential. By adopting such an electrode arrangement, oral muscles on the tip of the tongue can be trained more effectively when a current is applied to the electrodes.

[0031] Fig. 7 shows an image diagram of electrode arrangement in another embodiment. As shown in Fig. 7, in the oral muscle training device 1b, a first intraoral stimulating electrode 21 and a second intraoral stimulating electrode 22 are arranged on the tongue 7a of a user 7 to the left of the midline 7c, with the first intraoral stimulating electrode 21 arranged at the back of the tongue and the second intraoral stimulating electrode 22 arranged at the tip of the tongue. Furthermore, a cutaneous stimulating electrode 30a is arranged on the skin of the neck 7b of the user 7, opposite the first intraoral stimulating electrode 21 and the second intraoral stimulating electrode 22 across the midline 7c. The first intraoral stimulating electrode 21 and the cutaneous stimulating electrode 30a are at opposite potentials, and the second intraoral stimulating electrode 22 and the cutaneous stimulating electrode 30a are at the same potential. The arrangement of the three electrodes may be reversed, such as by arranging the first intraoral stimulation electrode 21 and the second intraoral stimulation electrode 22 on the right side of the midline 7c and the cutaneous stimulation electrode 30a on the left side. The intraoral stimulation electrode 21 and the second intraoral stimulation electrode 22 may be positioned at any desired distance, regardless of their positions. By adopting such an electrode arrangement, even with only one electrode under the chin or on the neck, applying a current to the electrode can selectively stimulate the central part of the tongue muscle.

[0032] Fig. 8 shows an image of electrode arrangement in another embodiment. As shown in Fig. 8, in the oral muscle training device 1c, a first intraoral stimulating electrode (21, 21a) and a second intraoral stimulating electrode 22 are arranged along the midline 7c on the tongue 7a of the user 7, with the first intraoral stimulating electrode 21 at the back of the tongue, the second intraoral stimulating electrode 22 in the middle of the tongue, and the first intraoral stimulating electrode 21a at the tip of the tongue. Thus, a pair of electrodes is three electrodes arranged at the tip, middle, and back of the tongue, and each pair is made up of the second intraoral stimulating electrode 22 in the middle of the tongue and the first intraoral stimulating electrode (21, 21a) at the tip and back of the tongue. In addition, a skin stimulating electrode 30 is arranged on the skin of the neck 7b of the user 7 so as to extend left and right around the midline 7c. The first intraoral stimulating electrode 21 and the first intraoral stimulating electrode 21a are at the same potential, and the second intraoral stimulating electrode 22 and the cutaneous stimulating electrode 30 are at the same potential. Furthermore, the first intraoral stimulating electrode (21, 21a) and the second intraoral stimulating electrode 22 and the cutaneous stimulating electrode 30 are at opposite potentials. In this way, by providing three electrodes on the tongue and arranging the first intraoral stimulating electrodes (21, 21a) so as to sandwich the second intraoral stimulating electrode 22, when a current is applied to the electrodes, the current density directly below the first intraoral stimulating electrode 21 and the second intraoral stimulating electrode 22 or the first intraoral stimulating electrode 21a and the second intraoral stimulating electrode 22 is increased, thereby enabling effective training of the oral muscles.

[0033] FIG. 9 shows an electrode arrangement image diagram of another embodiment. As shown in FIG. 9 , in the oral muscle training device 1d, first intraoral stimulating electrodes (21b, 21c) and second intraoral stimulating electrodes (22b, 22c) are arranged on the tongue 7a of a user 7. The first intraoral stimulating electrode 21b and the first intraoral stimulating electrode 21c are at the same potential, and the second intraoral stimulating electrodes 22b, 22c, and the skin stimulating electrode 30 are at the same potential. Furthermore, the first intraoral stimulating electrodes (21b, 21c) are at opposite potentials to the second intraoral stimulating electrodes (22b, 22c) and the skin stimulating electrode 30. That is, the first intraoral stimulating electrodes (21b, 21c) and the second intraoral stimulating electrodes (22b, 22c) are arranged so that adjacent electrodes have opposite polarities. In this embodiment, the pair of electrodes is composed of a first intraoral stimulation electrode (21b, 21c) and a second intraoral stimulation electrode (22b, 22c), with adjacent electrodes having opposite polarities. Furthermore, skin stimulation electrodes 30 are arranged on the skin of the neck 7b of the user 7, extending left and right around the midline 7c. By providing four electrodes on the tongue and arranging them so that adjacent electrodes have opposite polarities, when a current is applied to the electrodes, the current density directly below the first intraoral stimulation electrode 21b and the second intraoral stimulation electrode 22b, the first intraoral stimulation electrode 21b and the second intraoral stimulation electrode 22c, the first intraoral stimulation electrode 21c and the second intraoral stimulation electrode 22b, or the first intraoral stimulation electrode 21c and the second intraoral stimulation electrode 22c is increased, enabling effective training of oral muscles over a wide area corresponding to the area of ​​the four electrodes. In addition, only one electrode under the chin or on the neck is required, and by widening the electrode width, current can be passed over a wider area for stimulation.

[0034] Figure 10 is an image diagram of electrode arrangements in another embodiment, showing (1) two electrodes, (2) three electrodes, and (3) four electrodes placed on the tongue. The oral muscle training device 1e is a device in which the electrode arrangement of any of the oral muscle training devices (1, 1c, 1d) is rotated through a range of 180°. In the example shown in Figure 10(1), the first intraoral stimulation electrode 21 placed at the back of the tongue and the second intraoral stimulation electrode 22 placed at the tip of the tongue are rotated through a range of 180°. By setting the angle θ, the location of high sublingual current density can be changed. In the example shown in Fig. 10(2), the first intraoral stimulation electrode 21 placed at the back of the tongue, the second intraoral stimulation electrode 22 placed in the middle of the tongue, and the first intraoral stimulation electrode 21a placed at the tip of the tongue are rotated within a range of 180°, and in the example shown in Fig. 10(3), the first intraoral stimulation electrodes (21b, 21c) and the second intraoral stimulation electrodes (22b, 22c), which are arranged so that adjacent electrodes have opposite polarities, are rotated within a range of 180°. In such a case, the location of high sublingual current density can be changed by setting the angle θ.

[0035] 11A and 11B are schematic diagrams of electrode arrangements in another embodiment, in which the electrode placed on the skin surface is branched into two. (1) shows a first intraoral stimulating electrode placed at the back of the tongue and a second intraoral stimulating electrode placed at the tip of the tongue, and (2) shows a case in which the first intraoral stimulating electrode is placed at the tip of the tongue and a second intraoral stimulating electrode is placed at the back of the tongue. As shown in Fig. 11A, in the oral muscle training device 1f, the first intraoral stimulating electrode 21 and the second intraoral stimulating electrode 22 are placed along the midline 7c on the tongue 7a of the user 7, with the second intraoral stimulating electrode 22 placed at the tip of the tongue and the first intraoral stimulating electrode 21 at the back of the tongue. Furthermore, skin stimulating electrodes (30b, 30c) are placed on the skin of the neck 7b of the user 7, symmetrically with respect to the midline 7c. As shown in FIG. 11 (2), in the oral muscle training device 1g, the first intraoral stimulating electrode 21 and the second intraoral stimulating electrode 22 are positioned along the midline 7c on the tongue 7a of the user 7, with the first intraoral stimulating electrode 21 positioned at the tip of the tongue and the second intraoral stimulating electrode 22 positioned at the back of the tongue. Furthermore, the skin stimulating electrodes (30b, 30c) are positioned on the skin of the neck 7b of the user 7, symmetrically with respect to the midline 7c. Thus, in the oral muscle training devices (1f, 1g), the skin stimulating electrodes (30b, 30c) are not positioned on the midline 7c, but are positioned symmetrically with respect to the midline 7c. Therefore, when a current is applied to the electrodes, the current flows vertically along the midline 7c of the user 7, effectively stimulating the deep muscles in the oral cavity. This effect is also true for Examples 8 to 10, which will be described later.

[0036] In both oral muscle training devices (1f, 1g), the second intraoral stimulating electrode 22 and the skin stimulating electrodes (30b, 30c) are at the same potential. Furthermore, the first intraoral stimulating electrode 21, the second intraoral stimulating electrode 22, and the skin stimulating electrode (30b, 30c) are at opposite potentials. By adopting such an electrode arrangement, a wide range of oral muscles can be selectively trained. In this embodiment, an even number of electrodes are placed on the skin surface, and therefore, they are arranged symmetrically with respect to the midline 7c. In contrast, when an odd number of electrodes are placed on the skin surface, for example, when three electrodes are placed on the skin of the user's neck 7b, one electrode is placed on the midline 7c and the other electrodes are arranged symmetrically with respect to the midline 7c.

[0037] Fig. 12 shows an image of electrode arrangement in another embodiment. As shown in Fig. 12, in the oral muscle training device 1h, a first intraoral stimulating electrode (21, 21a) and a second intraoral stimulating electrode 22 are arranged along the midline 7c on the tongue 7a of the user 7, with the first intraoral stimulating electrode 21 at the back of the tongue, the second intraoral stimulating electrode 22 in the middle of the tongue, and the first intraoral stimulating electrode 21a at the tip of the tongue. Thus, in this embodiment, a pair of electrodes is three electrodes arranged at the tip, middle, and back of the tongue, and each pair is composed of the second intraoral stimulating electrode 22 in the middle of the tongue and the first intraoral stimulating electrode (21, 21a) at the tip and back of the tongue. In addition, skin stimulating electrodes (32a, 32b) are arranged branching out to the left and right on the skin of the neck 7b of the user 7. The cutaneous stimulation electrodes (32a, 32b) are electrodes branched from the first intraoral stimulation electrode (21, 21a) and placed on the skin surface. The cutaneous stimulation electrodes (32a, 32b) and the first intraoral stimulation electrode (21, 21a) are at the same potential, while the cutaneous stimulation electrodes (32a, 32b), the first intraoral stimulation electrode (21, 21a), and the second intraoral stimulation electrode 22 are at opposite potentials. In this way, by providing three electrodes on the tongue and placing the first intraoral stimulation electrodes (21, 21a) so as to sandwich the second intraoral stimulation electrode 22, the current density directly below the first intraoral stimulation electrode 21 and the second intraoral stimulation electrode 22, or the first intraoral stimulation electrode 21a and the second intraoral stimulation electrode 22, is increased, thereby enabling effective training of oral muscles over a long range corresponding to the length of the three electrodes. Furthermore, by arranging the skin stimulation electrodes (32a, 32b) branching out to the left and right, it is possible to train a wide range of oral muscles.

[0038] Fig. 13 shows an image of electrode arrangement in another embodiment. As shown in Fig. 13, in the oral muscle training device 1i, first intraoral stimulating electrodes (21b, 21c) and second intraoral stimulating electrodes (22b, 22c) are arranged on the tongue 7a of a user 7. The first intraoral stimulating electrode 21b and the first intraoral stimulating electrode 21c are at the same potential, and the second intraoral stimulating electrode 22b, the second intraoral stimulating electrode 22c, the skin stimulating electrode 30b, and the skin stimulating electrode 30c are at the same potential. Furthermore, the first intraoral stimulating electrodes (21b, 21c) are at opposite potentials to the second intraoral stimulating electrodes (22b, 22c) and the skin stimulating electrodes (30b, 30c). That is, the first intraoral stimulation electrodes (21b, 21c) and the second intraoral stimulation electrodes (22b, 22c) are arranged so that adjacent electrodes have opposite polarities. In this embodiment, a pair of electrodes is composed of a first intraoral stimulation electrode (21b, 21c) which is a plurality of electrodes and a second intraoral stimulation electrode (22b, 22c) which is a plurality of electrodes, and adjacent electrodes have opposite polarities. In addition, skin stimulation electrodes (30b, 30c) are arranged branching out to the left and right on the skin of the neck 7b of the user 7.

[0039] In this way, by providing four electrodes on the tongue and arranging adjacent electrodes as opposite polarities, when a current is applied to the electrodes, the current density directly below the first intraoral stimulating electrode 21 b and the second intraoral stimulating electrode 22 b, the first intraoral stimulating electrode 21 b and the second intraoral stimulating electrode 22 c, the first intraoral stimulating electrode 21 c and the second intraoral stimulating electrode 22 b, or the first intraoral stimulating electrode 21 c and the second intraoral stimulating electrode 22 c is increased, thereby enabling effective training of oral muscles over a wide range corresponding to the area of ​​the four electrodes. In addition, the arrangement of the cutaneous stimulating electrodes (30 b, 30 c) facilitates selective training of oral muscles.

[0040] Figure 14 is an image diagram of electrode arrangements in another embodiment, showing (1) two electrodes, (2) three electrodes, and (3) four electrodes placed on the tongue. The oral muscle training device 1j is an oral muscle training device in which the electrode arrangement of one of the oral muscle training devices (1f, 1h, 1i) is rotated through a range of 180°. In the example shown in Figure 14(1), the first intraoral stimulation electrode 21 placed at the back of the tongue and the second intraoral stimulation electrode 22 placed at the tip of the tongue are rotated through a range of 180°. By setting the angle θ, the location of high sublingual current density can be changed. In the example shown in Fig. 14(2), the first intraoral stimulation electrode 21 placed at the back of the tongue, the second intraoral stimulation electrode 22 placed in the middle of the tongue, and the first intraoral stimulation electrode 21a placed at the tip of the tongue are rotated within a range of 180°, and in the example shown in Fig. 14(3), the first intraoral stimulation electrodes (21b, 21c) and the second intraoral stimulation electrodes (22b, 22c), which are arranged so that adjacent electrodes have opposite polarities, are rotated within a range of 180°. In such a case, the location of high sublingual current density can be changed by setting the angle θ.

[0041] FIG. 15 shows a functional block diagram of an oral muscle training device according to another embodiment. FIG. 16 shows a schematic diagram of the oral muscle training device. As shown in FIG. 15 , the oral muscle training device 10 includes an oral stimulation device 20, a skin surface stimulation device 3, and a stimulation current generator 4. The oral stimulation device 20 includes a pair of electrodes disposed in the oral cavity: a first intraoral stimulation electrode 21, a second intraoral stimulation electrode 22, and a mouthpiece 24. As shown in FIG. 16 , the first intraoral stimulation electrode 21 and the second intraoral stimulation electrode 22 are attached and fixed to the mouthpiece 24. The remaining configuration is the same as that of the oral muscle training device 1 of Example 1. By fixing the first intraoral stimulation electrode 21 and the second intraoral stimulation electrode 22 to the mouthpiece 24, the user can fix the intraoral stimulation electrodes (21, 22) in appropriate positions simply by wearing the mouthpiece 24, thereby improving the training effect and convenience.

[0042] FIG. 17 shows an image diagram of the electrode arrangement of this embodiment. Moreover, FIG. 18 shows an image diagram of the electrode arrangement of another embodiment. Note that in FIGS. 17 and 18, for convenience of explanation, only an image of the arrangement of electrodes in the device is shown, and an image of the shape of the electrodes is deformed. The oral muscle training device 1k according to this embodiment includes a first pair of electrodes (21d, 22d) arranged on the tongue, a first surface electrode (skin stimulation electrode 30d) branched from one of the first pair of electrodes (22d) and arranged on the front of the neck, an electrical circuit for passing a first medium-frequency current between the electrodes consisting of the first pair of electrodes (21d, 22d) and the first surface electrode (30d), and a similar electrical circuit for passing a second medium-frequency current between the electrodes consisting of a second pair of electrodes (21e, 22e) arranged on the tongue, a second surface electrode (skin stimulation electrode 30e) branched from one of the second pair of electrodes (22e) and arranged on the front of the neck, and the second pair of electrodes (21e, 22e) and the second surface electrode (30e). The first and second surface electrodes, i.e., the skin stimulation electrodes (30d, 30e), are arranged symmetrically with respect to the midline 7c.

[0043] That is, the oral muscle training device 1k is composed of a first pair of electrodes (21d, 22d) placed on the tongue 7a of the user 7, a first surface electrode (skin stimulating electrode 30d) branched from one of the first pair of electrodes (22d) and placed on the front of the neck, and a first channel consisting of an electrical circuit that passes a first medium frequency (e.g., 5050 Hz) current between the electrodes consisting of the first pair of electrodes (21d, 22d) and the first surface electrode (30d), and a second channel consisting of an electrical circuit that passes a second medium frequency (e.g., 5000 Hz) current between the electrodes consisting of the second pair of electrodes (21e, 22e) and the second surface electrode (30e) branched from one of the second pair of electrodes (22e) and placed on the front of the neck. For example, if the first medium frequency current flowing through the first channel is 5050 Hz and the second medium frequency current flowing through the second channel is 5000 Hz, an interference wave of 50 Hz, the difference in frequency, will be generated, causing a large amount of current to flow between the intraoral electrode and the surface electrode on the front of the neck.This interference wave can be used to stimulate oral muscles such as the genioglossus.The first medium frequency current and the second medium frequency current may be the same frequency, in which case no interference wave will be generated.

[0044] Here, the first surface electrode (skin stimulation electrode 30d) is branched from one electrode (22d) of the first pair of electrodes (21d, 22d), but it may also be branched from the electrode (21d). Similarly, the second surface electrode (skin stimulation electrode 30e) is branched from one electrode (22e) of the second pair of electrodes (21e, 22e), but it may also be branched from the electrode (21e). Furthermore, the first and second surface electrodes, the skin stimulation electrodes (30d, 30e), are arranged symmetrically with respect to the midline 7c, but their positions may be reversed, or they may be arranged vertically on the midline 7c, as shown in FIG. 18. By arranging the skin stimulation electrodes (30d, 30e) vertically on the midline 7c, the deep central muscles can be stimulated more effectively. Note that the skin stimulation electrodes (30d, 30e) may be placed upside down on the midline 7c, or may be placed under the chin. Further, regarding the arrangement of the first pair of electrodes (21d, 22d) and the second pair of electrodes (21e, 22e), the tip of the tongue and the back of the tongue may be interchanged, respectively.

[0045] FIG. 20 shows a functional block diagram of the oral muscle training device of this embodiment. As shown in FIG. 20, the oral muscle training device 1k comprises an oral cavity stimulation device 200, a skin surface stimulation device 300, and a stimulation current generator 400. The oral cavity stimulation device 200 includes a first pair of electrodes (21d, 22d), a second pair of electrodes (21e, 22e), and a mouthpiece 24. The skin surface stimulation device 300 includes skin stimulation electrodes (30d, 30e) and a fixing band 6. The stimulation current generator 400 is connected to the electrode 21d via a lead wire 5a and to the electrode 22d via a lead wire 5b. The skin stimulation electrode 30d is branched from the electrode 22d using a lead wire 5c and connected to the stimulation current generator 400. The stimulation current generator 400 is connected to the electrode 21e via a lead wire 5d and to the electrode 22e via a lead wire 5e. The skin stimulation electrode 30e is branched from the electrode 22e using a lead wire 5f and connected to the stimulation current generator 400.

[0046] Fig. 21 shows a schematic diagram of the oral muscle training device of this embodiment. As shown in Fig. 21, a first pair of electrodes (21d, 22d) and a second pair of electrodes (21e, 22e) are attached and fixed to a mouthpiece 24, and skin stimulation electrodes (30d, 30e) are attached and fixed to a fixing band 6. By fixing the electrodes to the mouthpiece 24 and the fixing band 6, the user can position and fix the electrodes in appropriate positions simply by wearing the mouthpiece 24 or the fixing band 6, thereby improving training effectiveness and convenience. Operation buttons (4a, 4b, and other buttons not shown) are provided for switching the first medium-frequency current ON / OFF, adjusting the frequency of the first medium-frequency current, switching the second medium-frequency current ON / OFF, and adjusting the frequency of the second medium-frequency current. Note that the difference in illustration of the lead wires (5a to 5c) and the lead wires (5d to 5f) in FIG. 21 is to clarify the distinction between the first channel and the second channel, and they are made of the same material.

[0047] Fig. 22 shows a schematic flow diagram of the oral muscle training method of this embodiment. As shown in Fig. 22, first, a first pair of electrodes (21d, 22d) is placed on the tongue in the oral cavity (step S11), and a second pair of electrodes (21e, 22e) is placed on the tongue in the oral cavity (step S12). Note that when the first pair of electrodes (21d, 22d) and the second pair of electrodes (21e, 22e) are attached to the mouthpiece 24, steps S11 and S12 are performed simultaneously. Next, a skin stimulation electrode (30d), which is a first surface electrode branched from one of the first pair of electrodes (21d, 22d), is placed on the skin surface of the front of the neck (step S13), and a skin stimulation electrode (30e), which is a second surface electrode branched from one of the second pair of electrodes (21e, 22e), is placed on the skin surface of the front of the neck (step S14). If the skin stimulation electrodes (30d, 30e) are fixed with the fixing band 6, steps S13 and S14 are performed simultaneously. Then, a first medium-frequency current is applied between the electrodes formed by the first pair of electrodes (21d, 22d) and the first surface electrode (30d), and a second medium-frequency current having a frequency slightly different from that of the first medium-frequency current is applied between the electrodes formed by the second pair of electrodes (21e, 22e) and the second surface electrode (30e) (step S15). Note that the order of steps S11 to S14 may be reversed.

[0048] FIG. 23 shows an image of the electrode arrangement of this embodiment. As shown in FIG. 23 , in the oral muscle training device 1m, two first intraoral stimulation electrodes 21f are arranged in parallel across the midline 7c on the tongue 7a of the user 7, and a second intraoral stimulation electrode 22f is arranged along the midline 7c. The first intraoral stimulation electrode 21f is arranged at the back of the tongue, and the second intraoral stimulation electrode 22f is arranged at the tip of the tongue. The two first intraoral stimulation electrodes 21f are arranged side by side to increase the size of the first intraoral stimulation electrode. Therefore, a single large-sized first intraoral stimulation electrode may be arranged, as in Example 14 described below. Furthermore, a skin stimulation electrode 33 is arranged on the skin of the neck 7b of the user 7 so as to cover substantially the entire circumference of the neck 7b. 23, three skin stimulation electrodes 33 are arranged at approximately equal intervals on the front side of the neck, but in reality, three skin stimulation electrodes 33 are also arranged at approximately equal intervals on the back side of the neck, and are arranged so as to cover approximately the entire circumference of the neck 7b as a whole. By providing the skin stimulation electrodes 30 around approximately the entire circumference of the neck 7b, it is possible to pass a medium-frequency current over a wide area to stimulate it. In addition, the current density of the electrodes arranged on the skin surface can be reduced, preventing obstruction of blood flow in the carotid artery.

[0049] Fig. 24 is a diagram illustrating the functions of the oral muscle training device of this embodiment. As shown in Fig. 24, in the oral stimulation device 2f, a positive or negative electrode is placed on the tongue 7a of a user 7, and an electrode branching from one electrode is placed at a position on the neck where oral muscles such as the tongue muscle and genioglossus muscle are sandwiched between the electrodes. As shown in an image 80 of current flow, oral muscles such as the tongue muscle and genioglossus muscle 70 are stimulated by a current flowing through the first oral stimulation electrode 21, the second oral stimulation electrode 22, and the skin stimulation electrode 33.

[0050] A current measurement test was conducted using the electrode arrangement of Example 13 (N=2). Tables 2 and 3 below show the voltage, current, and resistance values ​​of the intraoral stimulation electrode or skin stimulation electrode when current of each frequency was applied. Table 2 below shows the current measurement test results for subject A, and Table 3 below shows the current measurement test results for subject B. The applied current was a continuous wave of 4 kHz to 8 kHz. Furthermore, "sensation" refers to the qualitative stimulation intensity felt by subjects A and B during the test, quantitatively expressed on a five-point scale from 0 to 4.

[0051]

[0052]

[0053] As shown in Table 2, for subject A, the current flowing through the intraoral electrode was 4.8 mA at 4000 Hz, 6.0 mA at 6000 Hz, and 5.6 mA at 8000 Hz. In contrast, the current flowing through the electrode on the neck skin was 10.2 mA at 4000 Hz, 9.0 mA at 6000 Hz, and 9.5 mA at 8000 Hz, indicating that the current flowing through the skin stimulation electrode was greater. Furthermore, subject A felt the most stimulation at 4000 Hz. As shown in Table 3, for subject B, the current flowing through the intraoral electrode was 6.1 mA at 4000 Hz, 6.8 mA at 6000 Hz, and 6.6 mA at 8000 Hz. In contrast, the current values ​​flowing through the electrodes on the neck skin were 8.0 mA at 4000 Hz, 7.8 mA at 6000 Hz, and 7.8 mA at 8000 Hz, indicating that the current flowing through the skin stimulation electrodes was greater. Furthermore, subject B felt the most stimulation at 4000 Hz. Because electrodes in the oral cavity cause a high degree of discomfort, electrical stimulation must be as low a stimulation as possible to avoid discomfort. This test found that 4000 Hz was the frequency that stimulated the muscles and provided the least discomfort.

[0054] FIG. 25 shows an image of electrode arrangement in this embodiment. As shown in FIG. 25 , in the oral muscle training device 1n, a first intraoral stimulation electrode 210 and a second intraoral stimulation electrode 220 are arranged along the midline 7c on the tongue 7a of the user 7, with the first intraoral stimulation electrode 210 at the tip of the tongue and the second intraoral stimulation electrode 220 at the back of the tongue. Unlike the first intraoral stimulation electrode 21 of Example 1, the first intraoral stimulation electrode 210 of this embodiment is larger to the extent that it does not stimulate the emetic center and allows a predetermined distance to be maintained between it and the second intraoral stimulation electrode 220. Similarly, unlike the second intraoral stimulation electrode 22 of Example 1, the second intraoral stimulation electrode 220 is larger to the extent that a predetermined distance to the first intraoral stimulation electrode 210 can be maintained. In addition, a skin stimulation electrode 34 is arranged on the skin of the neck 7b of the user 7 so as to cover substantially the entire circumference of the neck 7b. Unlike the skin stimulation electrode 33, the skin stimulation electrode 34 is configured such that one electrode is wrapped around almost the entire circumference of the neck 7b. This allows for stimulation by passing a medium-frequency current over a wide area. In addition, the current density of the electrode placed on the skin surface can be reduced, preventing obstruction of blood flow in the carotid artery.

[0055] Fig. 26 is a diagram illustrating the functions of the oral muscle training device of this embodiment. As shown in Fig. 26, in the oral stimulation device 201, a positive or negative electrode is placed on the tongue 7a of the user 7, and an electrode branching from one of the electrodes is placed at the neck position where oral muscles such as the tongue muscle and genioglossus muscle are sandwiched between the electrodes, and as shown in an image 80 of current flow, oral muscles such as the tongue muscle and genioglossus muscle 70 are stimulated by a current flowing through the first oral stimulation electrode 21, the second oral stimulation electrode 22, and the skin stimulation electrode 34.

[0056] (Other Examples) The oral muscle training device in the above-described embodiments uses a continuous wave current as the medium-frequency current. However, a burst wave current may be used, in which a current of 3 kHz or more but less than 8 kHz, more preferably 3 kHz or more but less than 5 kHz, flows continuously for a predetermined period of time, followed by a period of no current for a predetermined period of time (e.g., 1 second or more). By intermittently applying the medium-frequency current, it is possible to prevent the tongue from being pulled toward the front teeth and becoming immobilized. Here, the state in which no current flows for a predetermined period of time (intermittent state) may refer to a state in which no current flows at all for 1 second or more, or the medium-frequency current may be used as a low-frequency intermittent wave of several Hz. It has been empirically shown that an intermittent medium-frequency current of 2 seconds or more is preferable for swallowing saliva.

[0057] It is generally known that 20-50 Hz leads to hypertrophy of fast-twitch muscles, while 4-8 Hz leads to hypertrophy of slow-twitch muscles. On the other hand, medium frequencies have the characteristic of low skin resistance and easy penetration into deep tissue, but effective stimulation leading to muscle hypertrophy is difficult. Therefore, medium frequencies are used to stimulate the deep genioglossus muscle. Using medium frequencies as intermittent waves at 4-8 Hz can stimulate slow-twitch muscles, while using medium frequencies as intermittent waves at 20-50 Hz can potentially stimulate fast-twitch muscles. Furthermore, intermittent use of medium frequencies at a low frequency of 100 Hz may potentially promote nerve regeneration.

[0058] The present invention can effectively stimulate the genioglossus muscle, a deep muscle in the oral cavity, and is useful as a sleep apnea treatment device using electrical stimulation. Furthermore, by adjusting the electrode size, current amount, and frequency to stimulate not only the genioglossus muscle but also the geniohyoid muscle, it is also useful for swallowing training using electrical stimulation.

[0059] 1, 1a to 1n, 10 Oral muscle training device 2, 20, 200, 201 Oral stimulation device 3,300 Skin surface stimulation device 4,400 Stimulating current generator 4a, 4b Operation button 4c Display unit 5a to 5f Lead wire 6 Fixing band 7 User 7a Tongue 7b Neck 7c Midline 7d Submental area 8, 80 Image (of current flow) 21, 21a to 21e, 210 First intraoral stimulation electrode 22, 22b to 22e, 220 Second intraoral stimulation electrode 23 Base 24 Mouthpiece 30, 30a to 30e, 31, 32a, 32b, 33, 34 Skin stimulation electrode 70 Genioglossus muscle

Claims

1. An oral muscle training device comprising: a pair of electrodes arranged on the upper surface of the tongue inside the oral cavity, at least one of the pair of electrodes arranged on the midline of the upper surface of the tongue; an electrode branched off from one of the pair of electrodes and arranged on the skin surface; and an electrical circuit that passes a medium frequency current between the electrodes.

2. 2. The oral muscle training device according to claim 1, wherein the electrodes placed on the skin surface are placed under the chin or on the front of the neck.

3. 2. The oral muscle training device according to claim 1, wherein the electrodes arranged on the skin surface are arranged around substantially the entire circumference of the neck.

4. 4. The oral muscle training device according to claim 2, wherein the pair of electrodes are arranged at the tip and the back of the tongue.

5. The oral muscle training device according to claim 2, characterized in that the electrodes arranged on the skin surface are branched into at least two, and when there is an even number of electrodes, they are arranged symmetrically about the midline, and when there is an odd number of electrodes, one electrode is arranged on the midline and the other electrode is arranged symmetrically about the midline.

6. 4. The oral muscle training device according to claim 2, wherein the pair of electrodes is three electrodes arranged at the tip, middle and back of the tongue, and a pair is formed by an electrode in the middle of the tongue and an electrode at the tip and back of the tongue.

7. 4. The oral muscle training device according to claim 2, wherein the pair of electrodes is a plurality of pairs of electrodes, and adjacent electrodes have opposite polarities.

8. 2. The oral muscle training device according to claim 1, wherein the medium frequency current is a continuous wave current having a frequency of 3 kHz or more and less than 8 kHz.

9. 2. The oral muscle training device according to claim 1, wherein the medium frequency current is an intermittent wave in which a current of 3 kHz or more and less than 8 kHz flows continuously for a predetermined period of time, followed by a period of no current.

10. a first pair of electrodes arranged on an upper surface of the tongue in the oral cavity, at least one of the first pair of electrodes being arranged on the midline of the upper surface of the tongue; a first surface electrode branched off from one of the first pair of electrodes and arranged on the skin surface; and an electric circuit that passes a first medium frequency current between the electrodes consisting of the first pair of electrodes and the first surface electrode; a second pair of electrodes arranged on an upper surface of the tongue in the oral cavity, at least one of the second pair of electrodes being arranged on the midline of the upper surface of the tongue; a second surface electrode branched off from one of the second pair of electrodes and arranged on the skin surface; and an electric circuit that passes a second medium frequency current between the electrodes consisting of the second pair of electrodes and the second surface electrode; An oral muscle training device comprising:

11. 11. The oral muscle training device of claim 10, wherein the first and second surface electrodes are positioned under the chin or on the front of the neck.

12. An electrode set comprising an electrode placed in the oral cavity and an electrode placed on the skin surface in the oral muscle training device according to any one of claims 1 to 3, 10 and 11.

13. A step of placing a pair of electrodes on a tongue surface in the oral cavity, and placing at least one of the pair of electrodes on a midline of the tongue surface; A step of placing an electrode branched from one of the pair of electrodes on a skin surface under the chin or on the front of the neck, or on a skin surface around substantially the entire neck; Passing a medium frequency current between the electrodes; An oral muscle training method comprising:

14. placing a first pair of electrodes on a tongue surface in the oral cavity, with at least one electrode of the first pair of electrodes being positioned on a midline of the tongue surface; placing a second pair of electrodes on a tongue surface in the oral cavity, with at least one electrode of the second pair of electrodes being positioned on a midline of the tongue surface; A step of placing a first surface electrode branched from one of the first pair of electrodes on a skin surface under the chin or on the front of the neck; A step of placing a second surface electrode branched from one of the electrodes of the second pair of electrodes on a skin surface under the chin or on the front of the neck; A step of passing a first intermediate frequency current between electrodes constituted by a first pair of electrodes and a first surface electrode, and a second intermediate frequency current between electrodes constituted by a second pair of electrodes and a second surface electrode; An oral muscle training method comprising:

15. 4. The oral muscle training device according to claim 2, wherein the electrodes arranged on the skin surface are arranged on the midline.

16. 4. The oral muscle training device according to claim 2, wherein the size of the electrodes placed on the skin surface is larger than the size of the electrodes placed inside the oral cavity.