Relationship between respiratory muscle strength and dynamic balance in older persons requiring care or support: Focusing on the maximal single step length test and maximal double step length test as dynamic balance indices.

BACKGROUND: Falls are a major health problem. The relationship between dynamic balance related to falls and respiratory muscle strength related to sarcopenia and frailty is poorly understood. RESEARCH QUESTION: How do dynamic balance measures, such as maximal single step length test (MSL) and maximal double step length test (MDST), and respiratory muscle strength measures, such as maximal inspiratory (PImax) and maximal expiratory (PEmax), related to the requirement for long-term care or support in older people who live in the community? METHODS: This was a cross-sectional study of 39 older people (17 men, 22 women) aged ≥ 65 years community-dwelling who were certified as requiring long-term care or support under the Japanese system. The participants' PImax, PEmax, MSL, and MDST results were recorded. The measurement data were evaluated using Pearson's correlation coefficients and multiple regression analysis. RESULTS: MDST showed a positive correlation with PImax (r = 0.430, p = 0.006) but no correlation with PEmax. MSL showed no correlation with PImax or PEmax. A positive correlation was found between MDST and MSL (r = 0.851, p < 0.001), and multiple regression analysis with MDST as the dependent variable and PImax and MST as independent variables showed significant differences for MSL (p < 0.001) and PImax (p = 0.027). SIGNIFICANCE: In older people requiring long-term care or support, MDST had a greater association with inspiratory muscle strength compared with MSL. These results suggest the importance of inspiratory muscle strength training and MDST assessment in the prevention of falls in older people requiring long-term care or support.

Four minutes of capacitive and resistive electric transfer therapy increased jump performance.

Capacitive and resistive electric transfer (CRET) therapy can improve flexibility and increase muscle activity and may be useful as a warm-up technique. This study examined the effects of short-time CRET on jump performance. Thirty healthy men (age range, 20-40 years) were randomly divided into passive (n = 15) and active (n = 15) warm-up groups. The participants and statisticians were blinded to the participant allocation. The passive warm-up group underwent 4 min of CRET therapy on their posterior lower legs. The active warm-up group performed stretching and jogging for 4 min. Calf muscle temperature and rebound jump (RJ) index were measured before and after the intervention. The mean (± standard deviation) muscle temperature increased by 2.0 ± 0.5°C and 1.4 ± 0.6°C in the passive and active warm-up groups, respectively (p < 0.05). RJ index increased significantly in both groups (p < 0.05). Therefore, passive warm-up using CRET may help avoid energy loss while increasing the muscle temperature in a short time when compared with traditional active warm-up techniques.

Capacitive and resistive electric transfer (CRET) is a device with deep thermal effect. CRET therapy can improve flexibility and increase muscle activity and may be useful as a warm-up technique. This study examined the effects of short-time CRET on jump performance. Thirty healthy men (age range, 20­40 years) were randomly divided into passive (n=15) and active (n=15) warm-up groups. The passive warm-up group underwent 4min of CRET therapy on their calf. The active warm-up group performed stretching and jogging for 4min. Calf muscle temperature and jump performance were measured before and after the intervention. The mean (± standard deviation) muscle temperature increased by 2.0±0.5°C and 1.4±0.6°C in the passive and active warm-up groups, respectively (p<0.05). Jump performance increased significantly in both groups (p<0.05). Therefore, passive warm-up using CRET may help avoid energy loss while increasing the muscle temperature in a short time when compared with traditional active warm-up techniques.

Relationship between walking speed, respiratory muscle strength, and dynamic balance in community-dwelling older people who required long-term care or support and used a daycare center.

Background: Focusing on the relationship between frail older people and gait speed is vital to minimize the need for long-term care or increased support. The relationship between gait speed, respiratory muscle strength, and dynamic balance, is not well understood in older people requiring long-term care or support. Therefore, this study aimed to provide new insights into the relationship between gait speed, respiratory muscle strength, and dynamic balance in community-dwelling older people who required long-term care or support and used a daycare center. Methods: This was a cross-sectional study of 49 community-dwelling older people (21 men, 28 women) aged ≥65 years who were certified as requiring long-term care or support under the Japanese system. The participants' maximal inspiratory pressure (PImax), maximal expiratory pressure (PEmax), walking speed (maximal and normal walking speed), and maximal double-step length test (MDST) results were recorded. The measurement data were evaluated using Pearson's correlation coefficient and multiple regression analysis. Results: Pearson's correlation coefficient revealed correlations between PImax and the following: maximal walking speed (r = 0.606, p < 0.001), normal walking speed (r = 0.487, p < 0.001), and MDST (r = 0.435, p = 0.002). Correlations were also observed between PEmax and the following: maximal walking speed (r = 0.522, p < 0.001), normal walking speed (r = 0.467, p < 0.001), and MDST (r = 0.314, p = 0.028). Moreover, a correlation was found between MDST and both maximal walking speed and (r = 0.684, p < 0.001) and normal walking speed (r = 0.649, p < 0.001). The effect size was 0.379. Multiple regression analysis using a forced entry method with maximal walking speed as the dependent variable showed that maximal walking speed was significantly associated with MDST (p < 0.001) and PEmax (p = 0.036), with an effect size of 0.272. The model's adjusted coefficient of determination was 0.593 (p < 0.001). Multiple regression analysis using a forced entry method with normal walking speed as the dependent variable showed that normal walking speed was significantly associated with MDST (p < 0.001) and PEmax (p = 0.021), with an effect size of 0.272. The model's adjusted coefficient of determination was 0.497 (p < 0.001). Multiple regression analysis using a forced entry method with MDST as the dependent variable showed that MDST was significantly associated with PImax (p < 0.025), with an effect size of 0.243. The model's adjusted coefficient of determination was 0.148 (p = 0.017). Conclusions: Respiratory muscle strength and dynamic balance were related to walking speed in older people requiring long-term care or support.

Comparison of the effect of respiratory muscle strength on dynamic and static balance assessment between sarcopenia and non-sarcopenia groups.

[Purpose] We compared differences in the association between respiratory muscle strength and static and dynamic balance in sarcopenia and non-sarcopenia groups, for fall risk assessment. [Participants and Methods] The study included 37 participants aged ≥65 years, who were certified to receive long-term care. Inspiratory and expiratory muscle strength, hand grip strength, Timed Up and Go Test scores, and one-leg standing task scores were recorded. Pearson's correlation coefficients and multiple regression analysis were used for data analysis. [Results] Only the expiratory muscle and hand grip strength were correlated in the sarcopenia group. Expiratory and inspiratory muscle strength was correlated with both one-leg standing task scores and hand grip strength, and inspiratory muscle strength was correlated with the Timed Up and Go Test scores in the non-sarcopenia group. Multiple regression analysis revealed that expiratory muscle strength was an explanatory variable for the one-leg standing task and inspiratory muscle strength for the Timed Up and Go Test in the non-sarcopenia group. [Conclusion] Combined evaluation of expiratory muscle strength and the Timed Up and Go Test scores may be useful to assess the fall risk.

Effects of capacitive and resistive electric transfer therapy on pain and lumbar muscle stiffness and activity in patients with chronic low back pain.

[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.

Effect of electromyographic activity using capacitive and resistive electric transfer on non-specific chronic low back pain: a double-blind randomized clinical trial.

Capacitive and resistive electric transfer (CRET) therapy is used to reduce pain and improve functional disability, and the effect on low back pain remains to be investigated. This study aimed to examine the immediate effect on the onset time of the muscles after irradiating CRET therapy for non-specific chronic low back pain (NSCLBP). Thirty patients with NSCLBP were randomly divided into an intervention group (n = 15) and a sham group (n = 15). Participants and statisticians were blinded to participant allocation. The intervention group received one 15-minute session of CRET therapy on their lower back; the sham group similarly received one 15-minute session of sham therapy. Before and immediately after the intervention, the onset time of the trunk and lower limb muscles was measured during prone hip extension, and pain intensity was recorded using a visual analog scale. The intervention group showed a significant reduction in pain and a significantly earlier onset time of the thoracic part of the iliocostalis lumborum, lumbar part of the iliocostalis lumborum, lumbar multifidus, and gluteus maximus. These results showed that CRET therapy not only reduced pain, but also facilitated trunk muscle activity. Improvement in muscle activity patterns may improve activities of daily living. This study was registered at the University Hospital Medical Information Network in Japan (UMIN-CTR: 000046301).

Elucidation of abductor digiti minimi activity in chronic ankle instability.

[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.

Changes in the awareness and understanding of trunk muscle training in high school athletes.

[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.

Relationship between gait speed and trunk muscles in frail elderly individuals.

[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.

Is the diaphragm thickness related to gait speed in patients with hemiplegia caused by cerebrovascular accident?

[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.

Effect of low back pain on the muscles controlling the sitting posture.

[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.

Measurement of muscle length-related electromyography activity of the hip flexor muscles to determine individual muscle contributions to the hip flexion torque.

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 <0.005) and 60° (0.66 ± 0.17, p <0.001) and the SA at 60° (0.62 ± 0.24, p <0.005) were significantly decreased compared with those at 0°. However, the RMS value for the IL and RF did not change significantly. The RMS value and muscle length changes were significantly correlated in the IL (r =0.39, p <0.05), SA (r =0.51, p <0.001), and TFL (r =0.70, p <0.001), but not in the RF (r =0.22, p =0.180). We conclude that, in a hip joint flexed position, the contribution of the IL to hip flexion movement is relatively larger than that of the other hip flexor muscles.

Establishment of a recording method for surface electromyography in the iliopsoas muscle.

We examined the availability and reliability of surface electromyography (EMG) signals from the iliopsoas muscle (IL). Using serial magnetic resonance images from fifty healthy young males, we evaluated whether the superficial region of IL was adequate for attaching surface EMG electrodes. Subsequently, we assessed EMG cross-talk from the sartorius muscle (SA)-the nearest to IL-using a selective cooling method in fourteen subjects. The skin above SA was cooled, and the median frequencies of EMG signals from IL and SA were determined. The maximum voluntary contraction during isometric hip flexion was measured before and after selective cooling, and surface EMG signals from SA and IL were measured. The superficial area of IL was adequately large (13.2±2.7cm(2)) for recording surface EMG in all fifty subjects. The maximum perimeter for the medial-lateral skin facing IL was noted at a level 3-5cm distal to the anterior superior iliac spine. Following cooling, the median frequency for SA decreased significantly (from 70.1 to 51.9Hz, p<0.001); however, that for IL did not alter significantly. These results demonstrated that EMG cross-talk from SA was negligible for surface EMG signals from IL during hip flexion.