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[Purpose] This study aimed to compare the muscle activity around the foot and ankle joints, notably of the abductor digiti minimi, between affected and unaffected sides of individuals with chronic ankle instability. [Participants and Methods] Twelve adult males with chronic ankle instability in one ankle (age, 27.7 ± 5.4 years; height, 172.5 ± 8.1 cm; weight, 67.5 ± 8.1 kg) were included and underwent surface electromyography assessments in multiple positions on both affected and unaffected sides. Measurements were obtained for eight muscles including the abductor digiti minimi. Each measurement included a 5-s segment of the stable waveform, with the root mean square-processed and normalized to the resting position set to 1. [Results] Abductor digiti minimi activity on the affected side was significantly reduced during maximal toe extension/abduction with both ankle dorsiflexion and plantarflexion. Peroneus longus activity on the affected side was significantly greater during maximal toe extension/abduction with ankle plantarflexion; peroneus longus and tibialis anterior muscle activities were significantly greater on the affected side during maximal toe extension/abduction with ankle dorsiflexion. [Conclusion] In the absence of load, muscle imbalance in the intrinsic and extrinsic muscles of the foot was suggested. However, no significant differences were observed under loading conditions.

[Purpose] The external and internal abdominal muscles may be related to gait speed; however, this has not yet been elucidated. In this study, we aimed to clarify the relationship between gait speed and trunk muscle thickness in elderly individuals. [Participants and Methods] The participants were 12 elderly individuals (4 males and 8 females, mean age 83.4 years old, SD ± 0.5) that attend a day service center. We measured the 5 m free gait speed, the 5 m fastest gait speed, and the thickness of five trunk muscles (the rectus abdominis [divided into three parts: upper, central, and lower], external oblique, internal oblique, transverse abdominis, and iliopsoas muscles). [Results] There were positive correlations between the free gait speed and the thickness of the lower rectus abdominis, internal oblique, and transverse abdominis muscles. There were also positive correlations between the fastest gait speed and the thickness of the lower rectus abdominis, internal oblique, and transverse abdominis muscles. [Conclusion] Incorporating muscle strength training of the lower rectus abdominis, internal oblique, and transverse abdominis muscles into existing lower limb muscle training protocols is important to effectively maintain the gait speed of elderly individuals.

[Purpose] We aimed to determine the relationship between gait speed and diaphragm thickness in community-residing patients with hemiplegia caused by cerebrovascular accidents. [Participants and Methods] We recruited 11 elderly participants (six male and five female, mean age 71.1 ± 13.6 years) from an outpatient rehabilitation unit. The inclusion criteria were as follows: patients with hemiplegia caused by cerebrovascular accidents, those able to walk without assistance, and those able to understand our instructions. We measured the diaphragm thickness on both the paretic and non-paretic sides in each participant during maximum exhalation and inhalation during three laboured breaths by ultrasonography with a 7.5-MHz linear scanner. The liner scanner was placed on the eighth or ninth rib between the anterior and middle axillary lines. And their gait speed was measured during a 10 m walk. [Results] There was a strong positive correlation between gait speed and the ratio of diaphragm thickness between the paretic and the non-paretic sides during maximal inspiration. The other measured parameters did not show significant correlation with gait speed. [Conclusion] The symmetrical thickness of the diaphragm is a key factor in increasing gait speed in patients with hemiplegia. These findings may contribute to the development of trunk muscle strength-training programs that improve trunk function and gait speed in patients with hemiplegia.

[Purpose] This study aimed to compare the results of two questionnaires administered in 2013 and 2020, on the level of awareness and understanding of trunk muscle training. [Participants and Methods] In total, 238 soccer club members in high schools responded to our questionnaire regarding trunk muscle training. Two teams were recruited from the top (top 4), middle (top 16), and bottom levels (first-round losers), according to the prefectural tournament's results in 2019. This questionnaire comprised questions divided into four parts: 1. Prevalence of trunk muscle training; 2. Knowledge of the classification of trunk muscles (local and global); 3. Consciousness of local and global muscles during trunk muscle training; and 4. Knowledge of the role of each muscle. These results were compared to those obtained from the survey in 2013. [Results] A significant difference was observed only in the responses to question 2. Regarding question 2 in 2020, several student-athletes in the top-level teams were aware of muscle classification compared to those in the middle- and lower-level teams. [Conclusion] The number of athletes who understood the classification of trunk muscles increased significantly in 2020. Therefore, in the future, we would need to better educate young athletes concerning the purpose of trunk muscle training and the role of each muscle.

Background: Capacitive and resistive electric transfer (CRET) is becoming popular in sports settings. Although CRET is effective for improving pain and healing injured tissues, its influence on muscle function and morphology is still unclear. This study confirmed the immediate effects of CRET on the duration of muscular stiffness and the range of motion (ROM). Methods: This paper describes the protocol for a single arm trial with non-blinding of participants and researcher. Twenty-four healthy men participated in the study. They received CRET therapy for their lower back areas. The muscular stiffness of the multifidus muscle (superficial and deep) and the ROM using the active straight leg raise (ASLR) test were measured pre-intervention, post-intervention (immediately), and 15 minutes and 30 minutes post-intervention. We compared these parameters with one-way analysis of variance and Dunnett’s test (multiple comparison tests for subtests). Results: The muscular stiffness of the superficial and deep multifidus muscles became significantly lesser, and the ASLR test showed a significant increase compared to that obtained at pre-intervention. In addition, these effects persisted for 30 minutes. Conclusions: Warm-up is vital for improving muscular stiffness and for increasing the ROM. CRET is a useful device to achieve these aims as a passive warm-up method in sports settings.Trial registration number: UMIN000046304. Registered 7 December 2021 - Retrospectively registered, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000052845

[Purpose] In this study, we investigated the therapeutic effects of capacitive and resistive electric transfer therapy in patients with chronic low back pain. [Participants and Methods] The study included 24 patients with chronic low back pain (12 patients each in the intervention and sham groups). Pain intensity, superficial and deep lumbar multifidus stiffness and maximum forward trunk flexion and associated activation level of the iliocostalis (thoracic and lumbar component) and lumbar multifidus muscles were measured. [Results] Post-intervention pain intensity and muscle stiffness were significantly lower than pre-intervention measurements in the intervention group. However, no between-group difference was observed in the muscle activation level at the end-point of standing trunk flexion. [Conclusion] Our findings highlight a significant therapeutic benefit of capacitive and resistive electric transfer therapy in patients with chronic low back pain and muscle stiffness.

[Purpose] The purpose of the current study was to reveal the association between posture control and muscle activity by measuring the trunk and hip joint muscle activities in the upright and slump sitting positions in both the healthy participants and patients with recurrent lower back pain. [Participants and Methods] We recruited eleven patients of recurrent lower back pain and ten healthy participants. During the maintenance of the two types of posture, upright and slump, we collected the surface electromyography data. We assessed the following muscles: rectus abdominis, external oblique, thoracic erector spinae, lumbar erector spinae, internal oblique, lumbar multifidus, iliacus, serratus anterior, rectus femoris, tensor fascia latae, and gluteus maximus. We studied the differences in spinal-pelvic curvature and muscle activity between the upright and slump positions in each group. [Results] In the healthy group, comparison of the muscle activity in upright and slump positions for both the trunk (external oblique, internal oblique, lumbar erector spinae, and lumbar multifidus), and the hip muscles (iliacus and gluteus maximus) showed a significant decrease in activity in the slump position. In the group with recurrent lower back pain, although the external oblique, lumbar erector spinae and lumbar multifidus showed reduced activity in slump position, these values were smaller when compared to those in the healthy group. [Conclusion] This study aimed to clarify the relationship between posture (upright and slump) and the activity of the trunk and hip joint muscles in the healthy participants and the patients with recurrent lower back pain. The results indicated that postural changes caused by recurrent lower back pain significantly affected the activity of the muscles involved in controlling the posture.

This study aimed to investigate muscle length-related electromyography (EMG) of the iliopsoas (IL) and other hip flexor muscles to determine individual muscle contributions to the hip flexion torque. Ten healthy sedentary young men participated in the EMG experiment. A subgroup of six subjects underwent a magnetic resonance imaging (MRI) measurement to confirm the region of the skin over the IL. Surface EMG signals were sampled from the IL, rectus femoris (RF), sartorius (SA), and tensor fasciae latae (TFL) using an active electrode. The subjects performed maximum voluntary isometric hip flexion with the right hip joint set at -10°, 0°, 30°, and 60°. The root mean square (RMS) value for the TFL at 30° (0.81 ± 0.19, p