Objective: Kanshoho (Relaxation method by using stick pressure) is a technique that rapidly and painlessly relaxes muscles through light pressure applied to activated muscles. This study aimed to examine the effect of Kanshoho for muscle relaxation, clarify optimal pressing force and pressing area size, and investigate the influence of individual subject characteristics on Kanshoho muscle relaxation effects.
Methods: Thirty-nine consenting healthy adults performed voluntary seated lateral flexion for 5 minutes with a pressure bar applied to the right lumbar region. Five pressure bar forces (no force, 250 g, 500 g, 750 g, and 1,000 g) and three pressure bar diameters (1 cm, 2 cm, and 3 cm) were used. Lower back muscle hardness was measured immediately before and after exercise using a muscle hardness meter. Measurement value and rate of change in muscle hardness before and after exercise were compared for each pressing force and area condition. The influence of gender, BMI, and pre-intervention muscle stiffness on rate of change was also investigated.
Results: The measurement value of muscle hardness after exercise was lower than before exercise except the no force condition. The rate of change in muscle hardness of before and after exercise on 500 g and 750 g condition exhibited significantly lower than on no force and 250 g condition. The measurement value after exercise was lower than before exercise in all pressing area condition, however, the rate of change at 1 cm and 2 cm sizes showed significantly lower than at 3 cm size. The rate of change was not related to gender, BMI, or pre-intervention muscle stiffness.
Conclusion: A pressing force from 500 to 750 g on an area 1 to 2 cm in diameter produced the most relaxing effect in terms of reduced muscle tension. This Kanshoho technique would be applicable to a wide range of subjects without being affected by gender or body shape.

The purpose of this study was to examine whether motor unit behaviors would differ between in vastus medialis (VM) and vastus lateralis (VL), and between males and females. Seventy young healthy subjects (8females) performed a trapezoidal task with a target value of 60% of their maximum isometric knee extension strength. The EMG waveforms obtained from the VM and VL during the task were decomposed into individual motor unit action potential, and individual motor unit amplitude (MUAP_AMP) and firing rate (MFR) were calculated. In addition, the recruitment threshold (RT) of each motor unit was calculated using the knee extension torque. MUAP_AMP uses the average maximum amplitude of the rectified template waveform from each of the four electrodes. MFR is the inverse of the firing interval in the first quarter of the plateau period (5.0 s) during the trapezoid contraction task. The activity pattern of the motor unit is shown by the slope and intercept of the regression line obtained by scattering MUAP_AMP or MFR on the vertical axis and RT on the horizontal axis for each participant. The value of intercept of MUAP_AMP–RT were higher in males than in females and in the VL than in the VM, showing significant main effects of sex and muscle factors. The slope of MUAP_AMP–RT were steep in males than females, showing significant main effects of sex factors. The intercept value of MFR–RT was higher in females than in males and in the VM than in the VL, showing significant main effects of sex and muscle factors. The slope of the MFR–RT tended to be gentler in the VM in males and in the VL in females, indicating different VM and VL motor unit activity patterns by sex and a significant interaction between sex and muscle factors. These results indicate motor unit activity patterns in young healthy subjects and suggest that differences in sex and individual muscles must be taken into account to understand pathology-specific differences in motor unit activity patterns.

Muscle dysfunction remains semipermanent after Achilles tendon rupture. The main factors contributing to this are reduced force transmission function due to tendon scar healing and reduced muscle tension associated with tendon elongation. The relationship between these issues and the mechanobiological mechanisms of the tendon healing process remains unclear, preventing the establishment of physiotherapy strategies. This study aimed to elucidate the effects of reducing the tensile load on tendons after Achilles tendon rupture and suture on tendon lengthening, strength recovery, and collagen maturation. We used a mouse model in which mechanical stress on the tendon was controlled by joint immobilization and muscle paralysis. Muscle contraction-maintained mice showed that the tendon length ratio and the maximum failure force returned to the same level as on the non-operative side at 4 weeks after surgery. Contrastingly, muscle paralysis mice indicated that the tendon strength remained inferior, and the length was elongated compared to the non-operated side. On the other hand, collagen maturation and stress were still limited, even though muscle contraction was maintained under ankle immobilization. Our result suggested that unloading the tendon early after Achilles tendon rupture surgery, particularly restriction of muscle contraction, leads to structural changes in the tendon and contributes to permanent muscle weakness. This study reveals negative aspects of tendon unloading and the necessity of muscle contraction in early rehabilitation after Achilles tendon rupture and suture.