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.

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.

Objective: To develop the scale can evaluate change of condition of Total-Assisted Patients, and to explore its validity, reliability, and usefulness for predicting pressure sore risk.
Methods: We first developed the Scale for Total-Assisted Patients (STAP). The analysis was conducted as follows: the correlation and Mann-Whitney U Test of STAP score and FIM score, change of STAP score for 3 months and factor analysis, explore the reliability by intraclass correlation (ICC) and kappa, logistic regression was used to calculate the odds ratio (OR) with 95% confidence interval (CI) for assess the pressure sore risk.
Results: STAP was more suitable for total-assisted patients than FIM, 63.7% of patients with FIM 18 were observed STAP score change. Three factor were extracted from the factor analysis, “Limb range of motion”, “Amount of assistance with postural change”, “Consciousness”. Inter-rater reliability was ICC = 0.86, kappa = 0.95~0.99, OR = 0.83 (95% CI: 0.68–0.99, p=0.04).
Conclusion: STAP was more sensitive to change of condition of total-assisted patients than FIM, and STAP has high inter-rater reliability. Moreover STAP total score may be useful for predicting pressure sore risk.

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.

Neural factor, alongside muscular factor, are crucial elements to determine maximal muscle strength and an ability to control force. High-density surface electromyograph has been developed with novel algorithms to evaluate motor unit firing behaviors, which is the last pathway from the central nervous system to the muscle. Recent works reported that 1-year change in muscle strength in community-dwelling older adults could be explained by motor unit firing properties, and that older adults with low muscle mass has an abnormal motor unit firing pattern. Even though a significant increase in muscle mass was not observed after low-intensity weight-bearing squat training, a slight change in motor unit firing rate was observed. Thus, exercise effects on neuromuscular functions can be detected using the novel methods. If investigating the changes in motor unit firing behaviors, we could evaluate a time-of-day effect on motor unit firing properties, or acute effects of contraction mode on motor unit firing properties. An assessment of motor unit firing behavior can provide a detail mechanism of neuromuscular functions, such as muscle strength gain or control of muscle force.

Diabetes mellitus (DM) has been suggested to contribute to the onset of Alzheimer’s disease (AD) as a modifiable risk factor. Neurofibrillary tangles (NFTs), one of the neuropathological hallmarks of AD, are intracellular accumulations of phosphorylated tau protein. The number of NFTs in AD correlates with the severity of neuronal loss and cognitive decline, suggesting that tau protein is a direct contributor to neurodegeneration in these patients. We have investigated the effect of high-fat diet-induced diabetic conditions on tau phosphorylation in the brains of AD mice. We revealed a unique tau phosphorylation signature in the brains of diabetic AD mice. In addition, we identified six kinases that potentially mediate DM-induced tau phosphorylation in the brains of diabetic AD mice. These results suggest that DM contributes to the pathogenesis of AD through the phosphorylation of tau protein. This review describes the underlying mechanism linking DM and AD with a focus on changes in tau phosphorylation.

Walking is essential for maintaining independence in daily life, and aging is accompanied by an increased risk of falls, which often lead to severe injuries, reduced quality of life, and greater social and economic burdens. Elderly individuals generally exhibit slower walking speeds, strongly associated with reduced propulsive force. This reduction primarily results from age-related declines in plantar flexor power, which are partially compensated by increased proximal muscle recruitment. While such neuromuscular compensation enables gait continuation, it is also thought to destabilize gait; however, the underlying biomechanical mechanisms remain unclear. To explore these mechanisms, simple walking models provide valuable insights by abstracting human locomotion into its essential dynamics. The compass walking model demonstrates how hip stiffness and push-off impulse influence step length, cadence, and propulsive force. Extensions of this framework, such as knee-included models, further clarify the role of toe clearance, particularly minimum toe clearance (MTC), a critical determinant of tripping risk. Elderly individuals often show greater variability and lower values in MTC, yet its mechanical basis has not been fully explained. Simple models suggest that changes in hip stiffness and push-off modulation directly affect propulsion and MTC, thereby contributing to instability. This review highlights the significance of simple models as complements to detailed musculoskeletal simulations, offering intuitive insights into gait dynamics. Such approaches not only deepen the understanding of age-related gait instability but also inform fall-prevention strategies and the design of assistive technologies.

Although high iliotibial band (ITB) stiffness is commonly observed across knee disorders, their disease-specific characteristics and effective treatments remain unclear. This review synthesizes studies that used ultrasound shear wave elastography to quantify ITB stiffness in knee osteoarthritis (OA) and patellofemoral pain (PFP) and discusses the therapeutic potential of static stretching. Findings indicate that in patients with knee OA, ITB stiffness was higher than in asymptomatic older adults, and stiffness correlated with the external knee varus moment and the hip extension moment. For individuals with PFP, higher ITB tension was associated with a more lateral patellar position. A 5-minute static stretch performed with the hip in extension produced immediate reductions in ITB stiffness and improved patellar lateral alignment. In conclusion, increased ITB stiffness is a feature of some knee disorders, and static stretching may represent a therapeutic option. Further studies are needed to determine the long-term effects of static stretching and to develop objective assessment metrics.