Muscle strength improvement device and program

Abstract

A muscle strength improvement device 1 generates a sound stimulus for improving muscle strength, wherein the frequency of the sound stimulus is varied temporally.

Description

Muscle strength improvement equipment and programs

[0001] The present disclosure relates to techniques for improving muscle strength using sound stimulation.

[0002] The present inventors have discovered that sound stimulation has an effect on blood flow and have developed a blood flow promotion device that uses sound stimulation to promote blood flow (Patent Document 1). This blood flow promotion device promotes blood flow in the living body by generating sound stimulation (pure tone) with a constant frequency between 5 and 250 Hz, and is expected to be effective in improving symptoms caused by blood flow disorders such as sensitivity to cold, bedsores, Raynaud's syndrome, and diabetic anti-rust gangrene.

[0003] Furthermore, Non-Patent Document 1 shows that the blood flow rate of skeletal muscles, which is related to muscle strength, correlates with the blood flow rate of the skin.

[0004] International Publication No. 2020 / 129433

[0005] Bartlett, et al., “Impact of cutaneous blood flow on NIR-DCS measures of skeletal muscle blood flow index”, Journal of Applied Physiology, 2021

[0006] Therefore, the present inventors believed that the use of the conventional blood flow promotion device described in Patent Document 1 could also be expected to improve muscle strength, and so they tested the muscle strength improvement effect of sound stimulation on mice. Specifically, six mice were electrically stimulated in the hind limbs, causing the muscles to contract 50 times, and the contractile force during this period was measured. The mice were then allowed to rest for 24 hours. After the rest, three mice in the sound stimulation group (Sound) were stimulated for one minute with a pure tone at a sound pressure level of 85 dBZ and a frequency of 70 Hz, while three mice in the control group (Control) were not stimulated with sound stimulation. The mice then received the same electrical stimulation 50 times in the hind limbs, and the contractile force during this period was measured.

[0007] Figure 10(a) is a graph showing the contractile force in response to electrical stimulation before the break. Figure 10(b) is a graph comparing the contractile force (average value) of the control group and the sound stimulation group in the last five muscle contractions (46th to 50th) in response to electrical stimulation before the break, with the contractile force of the control group set to 1. Measurements taken before the break showed no significant difference in contractile force between the control group and the sound stimulation group. In other words, the control group and the sound stimulation group had roughly the same original muscle strength.

[0008] Figure 10(c) is a graph showing the contractile force in response to electrical stimulation after a break. Figure 10(d) is a graph comparing the contractile force (average value) of the control group and the sound stimulation group for the last five muscle contractions (46th to 50th) in response to electrical stimulation after a break, with the contractile force of the control group set to 1. There was no significant difference in contractile force between the control group and the sound stimulation group, even in measurements after a break. In other words, with the conventional blood flow promotion device, no improvement in muscle strength due to sound stimulation was observed.

[0009] The present disclosure has been made to solve the above problem, and aims to improve muscle strength through sound stimulation.

[0010] The present inventors have conducted extensive research in light of the above-mentioned problems, and have found that the above-mentioned problems can be solved by changing the frequency of the sound stimulation. That is, the present disclosure encompasses the following aspects. Item 1. A muscle strength improvement device that generates sound stimulation to improve muscle strength, wherein the frequency of the sound stimulation changes over time. Item 2. The muscle strength improvement device according to Item 1, wherein the frequency is 140 Hz or less. Item 3. The muscle strength improvement device according to Item 1, wherein the frequency is 100 Hz or less. Item 4. The muscle strength improvement device according to Item 1, wherein the difference between the maximum and minimum values ​​of the frequency is 60 Hz or less. Item 5. The muscle strength improvement device according to Item 1, wherein the difference between the maximum and minimum values ​​of the frequency is 10 Hz or less. Item 6. The muscle strength improvement device according to any one of Items 1 to 5, wherein the frequency changes periodically. Item 7. The muscle strength improvement device according to any one of Items 1 to 5, wherein the frequency changes continuously. Item 8. A program for causing a computer to realize a function of generating sound stimuli for improving muscle strength, the program comprising: a program for causing a computer to realize a function of generating sound stimuli for improving muscle strength, the program comprising ...

[0011] According to the present disclosure, muscle strength can be improved through sound stimulation.

[0012] 1A is a block diagram showing the configuration of a muscle strength improvement device 1 according to an embodiment of the present disclosure, and FIG. 1B is a schematic diagram showing the configuration of the muscle strength improvement device 1. (A) is a graph showing an example of a waveform of a sound stimulation, and (B) is a graph showing a modified waveform of a sound stimulation. (A) is a graph showing the rate of decrease in contractile force versus the number of muscle contractions before (before rest) and after stimulation for a pure tone stimulation group. (B) is a graph showing the average rate of decrease in contractile force in muscle contractions before and after stimulation for the 38th to 40th electrical stimulations for the pure tone stimulation group. (C) is a graph showing the rate of decrease in contractile force versus the number of muscle contractions before and after stimulation for a sweep sound stimulation group. (D) is a graph showing the average rate of decrease in contractile force in muscle contractions before and after stimulation for the 31st to 33rd electrical stimulations for the sweep sound stimulation group. (a) is a graph showing the contractile force versus the number of muscle contractions before and after stimulation for six normal mice (WT) without impaired inner ear function. (b) is a graph showing the contractile force versus the number of muscle contractions before and after stimulation for five inner ear-lesioned mice. (c) is a graph comparing the shift in average contractile force between before and after stimulation for the last six muscle contractions (75th to 80th contractions) between normal mice and inner ear-lesioned mice. (c) is a graph showing muscle strength (average contractile force) at the start of the experiment and during the first and second muscle strength tests for the tail-suspended / stimulation group, the tail-suspended / non-stimulation group, and the control group. (a) to (c) are cross-sectional images of the soleus muscle for the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group, respectively. (d) is a graph showing the average cross-sectional area of ​​the soleus muscle for the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group. (a) to (c) are cross-sectional images of the plantar muscles of the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group, respectively; (d) is a graph showing the proportion of slow-twitch muscle in the plantar muscles of the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group; and (e) is a graph showing the proportion of fast-twitch muscle in the plantar muscles of the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group. (a) and (b) are explanatory diagrams of an experiment (standing heel-raising test) to verify the effect of sound stimulation on muscle fatigue recovery in humans. (a) and (b) are graphs showing the evaluation results of muscle fatigue in the pure tone stimulation group and the sweep sound stimulation group, respectively.1 shows the muscle strength improving effect of sound stimulation using conventional technology, where (a) is a graph showing the contractile force in response to electrical stimulation before a break, (b) is a graph comparing the contractile force (average value) of the control group and the sound stimulation group for the last five muscle contractions (46th to 50th) in response to electrical stimulation before a break, (c) is a graph showing the contractile force in response to electrical stimulation after a break, and (d) is a graph comparing the contractile force (average value) of the control group and the sound stimulation group for the last five muscle contractions (46th to 50th) in response to electrical stimulation after a break.

[0024] ...

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the following embodiment, and various modifications are possible without departing from the spirit of the present disclosure.

[0014] Fig. 1(a) is a block diagram showing the configuration of a muscle strength improvement device 1 according to this embodiment, and Fig. 1(b) is a schematic diagram showing the configuration of the muscle strength improvement device 1. The muscle strength improvement device 1 has a function of generating sounds in a sound stimulation pattern for improving muscle strength. Hereinafter, the sounds themselves generated by the muscle strength improvement device 1 will be referred to as "sound stimulation."

[0015] The muscle strength improvement device 1 comprises an operation receiving unit 2 that receives operations for outputting sound stimulation, a setting unit 3 that sets the sound stimulation in accordance with the operation, a sound signal generating unit 4 that generates a signal for the set sound stimulation, and an output unit 5 that outputs the sound stimulation based on the generated signal.

[0016] The operation reception unit 2 is configured, for example, by a touch panel. The setting unit 3 and sound signal generation unit 4 are built into the main body 6. The sound signal generation unit 4 has a function of generating sound stimulation signals whose frequencies change over time, either continuously or intermittently over time.

[0017] The output unit 5 may be a speaker that outputs sound from the muscle strength improvement device 1 to the outside, or may output sound to a speaker connected to the muscle strength improvement device 1. The output unit 5 is provided near a region of the body where the muscle to be improved in muscle strength is located. As will be described later, the inner ear function does not contribute to the muscle strength improvement effect of sound stimulation, so the location of the region is not particularly limited and may be a region away from the ear.

[0018] For example, if the part (target part) where the muscles to be improved in muscle strength are located is an arm or a leg, the output unit 5 is placed near the arm or leg of the subject 7. In this case, it is preferable that the output unit 5 is not in contact with the arm or leg of the subject 7, and that vibrations from a speaker or the like that constitutes the output unit 5 are not directly transmitted to the target part. In this embodiment, the output unit 5 is held by a variable arm 8. Note that the target part is not limited to an arm or a leg, and any part of the subject's body where skeletal muscles are present (including the torso, face, etc.) can be the target.

[0019] Furthermore, because the inner ear function does not contribute to the muscle strength improvement effect of sound stimulation, it is preferable that the muscle strength improvement device 1 include a suppression unit 9 that suppresses the sound stimulation from reaching the ears of the subject. The suppression unit 9 is provided at any position between the output unit 5 and the ear, and can be composed of a member that blocks or absorbs sound.

[0020] 1A, each element described as a functional block that performs various processes can be configured in hardware by a circuit block, memory, or other LSI, and in software by a program loaded into memory, etc. Therefore, it will be understood by those skilled in the art that these functional blocks can be realized in various forms by hardware alone, software alone, or a combination thereof, and are not limited to any one of them.

[0021] As will be described in detail later, the muscle strength improvement device 1 generates sound stimuli whose frequency changes over time in order to improve muscle strength. The sound stimuli may be continuous sounds that are emitted continuously over time, or discontinuous sounds (intermittent sounds) that are emitted intermittently and / or periodically. The muscle strength improvement device 1 is installed as medical equipment in medical facilities such as hospitals, and is used, for example, to improve the symptoms of athletic patients who have muscle fatigue or injury. A doctor may be able to set the frequency range, the cycle time for frequency change, the sound pressure level, etc., depending on the severity of the patient's symptoms.

[0022] The muscle strength improvement device 1 may be commercially available as a health device and used for improving the muscle strength of able-bodied individuals. The muscle strength improvement device 1 is preferably formed compactly so that it can be carried around. By distributing the muscle strength improvement device 1 as a health device, it is possible to expect health promotion through physical training and improving physical condition, recovery from fatigue, prevention or improvement of locomotive syndrome, and beauty effects through improved strength of facial muscles.

[0023] In the present disclosure, "improving muscle strength" means that for multiple muscles that have the same muscle strength before stimulation, there is a significant difference (p value less than 0.05) between the muscle strength of a muscle that has been given the sound stimulation according to the present disclosure and the muscle strength of a muscle that has not been given the sound stimulation. Furthermore, in the present disclosure, improving muscle strength is a concept that also includes the effects of improving muscle fatigue, which improves muscle strength that has decreased due to muscle fatigue, and training muscles.

[0024] The sound stimulation generated by the muscle strength improvement device 1 is a sound stimulation whose frequency changes over time. Fig. 2(a) is a graph showing an example of the waveform of the sound stimulation. The frequency of this sound stimulation changes periodically with a cycle time P, but the frequency change does not have to be periodic. The frequency is not particularly limited as long as it is in the audible range (20 Hz or higher), but is preferably 90 Hz or lower. Furthermore, the frequency range, i.e., the difference between the maximum value Fmax and the minimum value Fmin, is not particularly limited, but is preferably 60 Hz or lower, and more preferably 10 Hz or lower.

[0025] Furthermore, the sound stimulus shown in Figure 2(a) has a frequency that changes continuously (gradually), and such a sound stimulus will be referred to as a "sweep sound" hereinafter. The change in frequency of the sweep sound does not have to be linear.

[0026] Furthermore, the frequency may change discontinuously, as in the sound stimulation shown in FIG. 2(b).

[0027] The sound pressure level of the sound stimulation should be 70 dBZ or higher, preferably 80 dBZ or higher, and more preferably 85 dBZ or higher. In this disclosure, "sound pressure level" refers to the sound pressure level without auditory correction. When used in humans, the sound pressure level refers to the sound pressure level at the location of the muscle targeted for muscle strength improvement. When used in mice, the sound pressure level is synonymous with the sound pressure level at the location where the mouse is located. In the following examples, the sound pressure level refers to the sound pressure level at the location where muscle strength is to be improved, rather than the output setting value.

[0028] 1, sound stimulation can be set by user operation, but the muscle strength improvement device 1 may be configured not to allow sound stimulation to be set. For example, the muscle strength improvement device may be configured to output only one type of sound stimulation by playing pre-stored audio data. Alternatively, the muscle strength improvement device may be realized by inputting audio data of sound stimulation for improving muscle strength into a general-purpose audio device or computer via a telecommunications line or a storage medium such as a compact disc or flash memory.

[0029] Through experiments and the like described below, the present inventors have discovered that sounds whose frequencies change over time are sound stimuli suitable for improving muscle strength.

[0030] Example 1 In Example 1, the muscle strength improvement effects of pure tone and sweep sound were evaluated using an evaluation system in which muscle fatigue was induced by continuous contraction of mouse muscles via electrical stimulation. Specifically, seven mice (9-10 weeks old, male) were prepared, and the muscles were contracted 40 times by electrical stimulation of the mouse's hind limbs, during which the contractile force was measured. The mice were then allowed to rest for 24 hours. After the rest, three mice in the pure tone stimulation group were given a one-minute stimulus of pure tone at a sound pressure level of 85 dBZ and a frequency of 85 Hz, and four mice in the sweep sound stimulation group were given a one-minute stimulus of sweep sound at a sound pressure level of 85 dBZ and a frequency ranging from 80 to 90 Hz, with a cycle time of 0.1 seconds. The mice were then given the same electrical stimulation 40 times in their hind limbs, during which the contractile force was measured.

[0031] Figure 3(a) is a graph showing the rate of decrease in contractile force versus the number of muscle contractions before (before rest) and after stimulation for the pure tone stimulation group. Figure 3(b) is a graph showing the average rate of decrease in contractile force for muscle contractions before and after stimulation for the 38th to 40th electrical stimulations for the pure tone stimulation group. This graph shows that pure tone stimulation did not have a significant effect on improving muscle strength.

[0032] Figure 3(c) is a graph showing the rate of decrease in contractile force versus the number of muscle contractions before and after stimulation in the sweep sound stimulation group. Figure 3(d) is a graph showing the average rate of decrease in contractile force during muscle contractions before and after stimulation in response to the 31st to 33rd electrical stimulations in the sweep sound stimulation group. This graph demonstrates that sweep sound stimulation significantly improved muscle strength. [Example 2] In Example 2, we used inner ear-damaged mice (VL) with impaired inner ear function to examine whether inner ear function contributes to the muscle strength improvement effect of sound stimulation. Specifically, 11 mice (2.5 months old, male) were prepared, and five of them were impaired by intratympanic administration of an ototoxic drug. Then, the hind limbs of the 11 mice were electrically stimulated to contract the muscles 80 times, and the contractile force during this period was measured. The mice were then allowed to rest for 24 hours, after which they were given a 5-minute sound sweep with a sound pressure level of 85 dBZ and a frequency ranging from 80 to 90 Hz, with a cycle time of 0.1 seconds. The mice were then given 80 similar electrical stimuli to their hind paws, and the contractile force during these stimuli was measured.

[0033] Figure 4(a) is a graph showing the contractile force versus the number of muscle contractions before and after stimulation for six normal mice (WT) with intact inner ear function, Figure 4(b) is a graph showing the contractile force versus the number of muscle contractions before and after stimulation for five inner ear-damaged mice, and Figure 4(c) is a graph comparing the shift in average contractile force between before and after stimulation for the last six muscle contractions (75th to 80th contractions) between normal mice and inner ear-damaged mice.

[0034] These results show that the muscle strength improvement effect of sweep sound stimulation was observed in both inner ear-damaged mice and normal mice, indicating that inner ear function does not contribute to the muscle strength improvement effect of sound stimulation.

[0035] Example 3 In Example 3, mice with reduced muscle strength due to tail suspension (a mouse model of locomotive syndrome) were used to verify the effect of sweep sound stimulation on improving muscle weakness. Specifically, 20 mice (7 weeks old) were prepared, and 11 of the mice were tail-suspended for two weeks to reduce hindlimb muscle strength. The 20 mice then underwent a first muscle strength test, measuring the contractile force of the final muscle contraction after 57 electrical stimuli were applied to the hindlimb. Furthermore, the paired tail suspension of the 11 mice was discontinued, and six of the mice with reduced muscle strength (the tail-suspended / stimulation group) were stimulated with sweep sound (sound pressure level: 85 dBZ, frequency: 60-120 Hz, cycle time: 0.1 s) for five minutes per day for one week. The researchers then performed a second muscle test on 20 mice, one week after the first test, in the same manner as the first.

[0036] Figure 5 is a graph showing muscle strength (average contractile force) at the start of the experiment and during the first and second muscle strength tests for the tail-suspended stimulation group, tail-suspended non-stimulation group, and control group. This graph shows that applying the sweep sound stimulus significantly improved muscle weakness.

[0037] Furthermore, after the second muscle strength test, the soleus and plantaris muscles of each mouse were stained with NADH-TR, the cross sections of these muscles were photographed, and the cross-sectional area of ​​each muscle was measured.

[0038] Figures 6(a) to 6(c) show cross-sectional images of the soleus muscle in the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group, respectively. Figure 6(d) is a graph showing the average cross-sectional area of ​​the soleus muscle in the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group. As observed in human locomotive syndrome, the cross-sectional area of ​​the soleus muscle in the tail-suspended / non-stimulation group was significantly reduced compared to the control group (non-tail-suspended group), indicating muscle atrophy. On the other hand, the cross-sectional area of ​​the soleus muscle in the tail-suspended / stimulation group was larger than that in the tail-suspended / non-stimulation group, indicating that applying a sweep sound stimulus has a recovery effect on the soleus muscle.

[0039] Figures 7(a)-(c) show cross-sectional images of the plantar muscles of the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group, respectively. Figure 7(d) is a graph showing the proportion of slow-twitch muscle fibers in the plantar muscles of the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group. Figure 7(e) is a graph showing the proportion of fast-twitch muscle fibers in the plantar muscles of the control group, the tail-suspended / non-stimulation group, and the tail-suspended / stimulation group. NADH-TR staining reflects mitochondrial activity in muscle fibers. In cross-sectional images, fast-twitch muscle fibers containing a large amount of glycolytic enzymes appear darker, while slow-twitch muscle fibers containing a large amount of aerobic enzymes appear lighter. The tail-suspended / non-stimulation group showed rapid muscle fatigue compared to the control group (non-tail-suspended group). Furthermore, the proportion of slow-twitch and fast-twitch muscle fibers in the tail-suspended / stimulation group was comparable to the control group, demonstrating a significant improvement due to the sweep sound stimulation.

[0040] Example 4 In Example 4, the muscle fatigue recovery effect of sweep sound stimulation was examined in healthy human subjects. Specifically, as shown in FIG. 8(a), two myoelectric potential sensors 10 were attached to the calves of both legs, and transient muscle fatigue was induced by repeating heel-raising exercises 30 times. The subjects were then seated to rest, and as shown in FIG. 8(b), a speaker 11 was placed 3 cm from the myoelectric potential sensor 10 on the left leg L and 40 cm from the myoelectric potential sensor 10 on the right leg R. During the rest period, a pure tone stimulation group of four subjects received a 70 Hz pure tone stimulation for five minutes, and a sweep sound stimulation group of six subjects received a 0.1 s frequency sweep sound stimulation for five minutes, with frequencies ranging from 60 to 120 Hz. The sound pressure level at the site where the myoelectric potential sensor 10 was attached on the left leg L of each subject was 85 dBZ. The sound pressure level at the site of the myoelectric potential sensor 10 on the right leg R was 70 dBZ for the pure tone stimulation group and 65 dBZ for the sweep sound stimulation group. After that, the muscle fatigue of each subject was evaluated by performing spectrum analysis on the myoelectric potential data measured by the myoelectric potential sensor 10.

[0041] 9(a) and (b) are graphs showing the evaluation results of muscle fatigue for the pure tone stimulation group and the sweep sound stimulation group, respectively. The vertical axis of the graph represents the average frequency shift of the myoelectric potential, with smaller values ​​indicating greater muscle fatigue. From these results, it was found that the sweep sound stimulation had a significant effect on muscle fatigue recovery in the sweep sound stimulation group, but not in the pure tone stimulation group.

[0042] Example 5 In Example 5, for the purpose of screening conditions for sound stimulation effective in improving muscle strength, the effects of increasing skin blood flow in mice were compared using the pure tone described in Patent Document 1, which has no change in frequency, and a sweep tone with a continuously changing frequency, using mouse skin blood flow as an index. Specifically, six mice (3-month-old males) were prepared and stimulated with a pure tone at a sound pressure level of 85 dBZ and a sweep tone at a sound pressure level of 85 dBZ, and the average skin blood flow increase rate in the hind limbs (calves) was measured before and after stimulation. The frequency range of the sweep tone (difference between the maximum and minimum values) was 10 Hz, and the frequency change period was 0.1 s. Similar measurements were then repeated while changing the frequency of the pure tone and the frequency range of the sweep tone.

[0043] Figure 11 is a graph showing the relationship between the frequency of sound stimulation given to mice and the rate of increase in skin blood flow. From these results, it was found that the rate of increase in blood flow of mice given a sweep sound was greater than the rate of increase in blood flow of mice given a pure tone with a frequency equal to the median of the frequency range of the sweep sound. Although frequencies of 100 Hz or higher are effective, it was found that a sweep sound of 90 Hz or less, and particularly a sweep sound that varies between 80 and 90 Hz, is remarkably effective in increasing blood flow.

[0044] Therefore, it was found that the sweep sound, if its frequency is 100 Hz or less, has a significantly greater effect on increasing blood flow than a pure tone of the same frequency level.

[0045] It is possible that the stage on which the mouse was placed vibrates due to the stimulus of the sweep sound, and that this vibration of the stage increases the blood flow in the mouse, but as shown in Figure 12, there was no significant difference in the vibration of the stage in any of the X, Y, or Z axes with or without the stimulus of the sweep sound. Therefore, it was confirmed that the increase in blood flow in the mouse was due to the sound stimulus, and not due to the vibration of the stage.

[0046] Example 6 In Example 6, the relationship between the period of change in frequency of the sweep sound (cycle time) and the effect of increasing skin blood flow was examined. Specifically, the six mice in Example 5 above were stimulated with seven types of sweep sound, with a sound pressure level of 85 dBZ, a frequency range of 80-90 Hz, and cycle times varying from 0.01 s to 10 s, and the average increase in skin blood flow in the hind limbs before and after stimulation was measured.

[0047] 13 is a graph showing the relationship between the cycle time of the sweep sound given to mice and the rate of increase in skin blood flow. This graph shows that the blood flow increasing effect is the same regardless of the cycle time of the sweep sound. Therefore, it was found that the change in frequency of the sweep sound can be either periodic or non-periodic.

[0048] Example 7 In Example 7, the relationship between the frequency and frequency range (difference between maximum and minimum values) of the sweep sound and the effect of increasing blood flow in muscle tissue was examined. Specifically, three mice (7-week-old, male) were prepared, and the skin tissue was removed under anesthesia to expose the muscle tissue. The blood flow in the muscle tissue was measured using a laser Doppler blood flow imaging device. First, the blood flow was measured for 10 seconds without applying sound stimulation, and this measurement result was used as the baseline. Then, 12 types of sweep sounds with different frequencies and frequency ranges were applied for 10 seconds each, and the blood flow in the muscle tissue during stimulation was measured.

[0049] 14 is a graph showing the relationship between the frequency range of the sweep sound given to mice and the rate of increase in muscle tissue blood flow. The horizontal axis of the graph represents the frequency range of the sweep sound, and the sound pressure level of each sweep sound was 85 dBZ. The vertical axis of the graph represents the rate of increase in blood flow (average value for three mice) from baseline. From these results, it was found that for sweep sounds with frequencies between 80 Hz and 130 Hz, sweep sounds with a frequency range of 10 Hz had a stronger effect of increasing blood flow than sweep sounds with a frequency range of 20 Hz.

[0050] [Additional Notes] Although the embodiments and examples of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and examples, and various modifications are possible within the scope of the claims. For example, the above embodiments and examples describe specific numerical values ​​such as the frequency of sound stimulation whose frequency changes over time, but the numerical values ​​of the frequency, etc. are not particularly limited as long as there is a significant difference between the muscle strength of a muscle that has received sound stimulation and the muscle strength of a muscle that has not received sound stimulation.

[0051] REFERENCE SIGNS LIST 1 Muscle strength improvement device 2 Operation reception unit 3 Setting unit 4 Sound signal generation unit 5 Output unit 6 Main body 7 Subject 8 Variable arm 9 Suppression unit 10 Myoelectric potential sensor 11 Speaker

Claims

1. A muscle strength improvement device that generates sound stimuli for improving muscle strength, A muscle strength improvement device in which the frequency of the sound stimulation changes over time.

2. The muscle strength improvement device according to claim 1 , wherein the frequency is 140 Hz or less.

3. The muscle strength improvement device according to claim 1 , wherein the frequency is 100 Hz or less.

4. The muscle strength improvement device according to claim 1 , wherein the difference between the maximum and minimum frequencies is 60 Hz or less.

5. The muscle strength improvement device according to claim 1 , wherein the difference between the maximum and minimum values ​​of the frequency is 10 Hz or less.

6. The muscle strength improvement device according to any one of claims 1 to 5, wherein the frequency changes periodically.

7. The muscle strength improvement device according to any one of claims 1 to 5, wherein the frequency changes continuously.

8. The muscle strength improvement device according to any one of claims 1 to 5, wherein the frequency is changed at a cycle time of 0.1 s to 10 s.

9. An output unit that outputs the sound stimulus, The muscle strength improvement device according to any one of claims 1 to 5, wherein the output unit is in non-contact with the subject through space.

10. A program for causing a computer to realize a function of generating sound stimuli for improving muscle strength, comprising: The frequency of the sound stimulus varies over time.

11. The frequency is between 70 Hz and 110 Hz, The muscle strength improvement device according to claim 1 , wherein the difference between the maximum and minimum values ​​of the frequency is 10 Hz or less.

12. The muscle strength improvement device according to claim 1 , wherein sound is applied to a part of the body that is a target for muscle strength improvement.