Neural Drive and Motor Unit Characteristics of the Serratus Anterior in Individuals With Scapular Dyskinesis.

OBJECTIVE: Scapular dyskinesis is one of the causes of shoulder disorders and involves muscle weakness in the serratus anterior. This study investigated whether motor unit (MU) recruitment and firing property, which are important for muscle exertion, have altered in serratus anterior of the individuals with scapular dyskinesis. METHODS: Asymptomatic adults with (SD) and without (control) scapular dyskinesis were analyzed. Surface electromyography (sEMG) waveforms were collected at submaximal voluntary contraction of the serratus anterior. The sEMG waveform was decomposed into MU action potential amplitude (MUAPAMP), mean firing rate (MFR), and recruitment threshold. MUs were divided into low, moderate, and high thresholds, and MU recruitment and firing properties of the groups were compared. RESULTS: High-threshold MUAPAMP was significantly smaller in the SD group than in the control group. The control group also exhibited recruitment properties that reflected the size principle, however, the SD group did not. Furthermore, the SD group had a lower MFR than the control group. CONCLUSIONS: Individuals with scapular dyskinesis exhibit altered MU recruitment properties and lower firing rates of the serratus anterior; this may be detrimental to muscle performance. Thus, it may be necessary to improve the neural drive of the serratus anterior when correcting scapular dyskinesis.

Effects of Gluteus Maximus Muscle Activity and Pelvic Width on Dynamic Frontal Plane Hip Joint Stiffness During Gait in Healthy Young Women.

CONTEXT: Excessive hip adduction and internal rotation are abnormal movements that may lead to the onset and progression of patellofemoral pain. Previous studies have reported that lower dynamic frontal plane hip joint stiffness in the gait of women is associated with the magnitude of hip adduction and internal rotation angles. However, the factors contributing to the lack of dynamic frontal plane hip joint stiffness in the gait of young women are unclear. This study aims to investigate the factors affecting dynamic frontal plane hip joint stiffness during the weight-acceptance phase of the gait of healthy young women. DESIGN: Cross-sectional study. METHODS: This study included 30 healthy women between the ages of 18 and 30 years. The pelvic width/femur length ratio was calculated by dividing the pelvic width by the femur length. Data on hip kinematics and kinetics and activation of the gluteus maximus and medius, tensor fasciae latae, and adductor longus muscles during gait were collected using a motion capture system, force plates, and surface electromyography. Stepwise multiple regression analysis was conducted to determine the extent to which each independent factor affected dynamic frontal plane hip joint stiffness. RESULTS: In healthy young women, decreased dynamic frontal plane hip joint stiffness was associated with decreased muscle activity of the gluteus maximus during the gait, as well as greater pelvic width/femur length ratio. CONCLUSIONS: Women with a relatively great pelvic width relative to femur length may have more difficulty in producing dynamic frontal plane hip joint stiffness. However, increasing the muscle activity of the gluteus maximus may contribute to increased dynamic frontal plane hip joint stiffness.

Movement control during one-leg standing is important for the bone mineral density maintenance or improvement.

INTRODUCTION: Both hip fracture and bone mineral density (BMD) decline on the non-fractured side are more likely to occur within 1 year. However, there are no longitudinal study reports on the factors associated with BMD maintenance or improvement within the first year after hip fracture. This study aimed to investigate the factors influencing the neck BMD maintenance or improvement in patients with hip fractures from within 2 weeks-6 months after surgery. MATERIALS AND METHODS: Patients were hip fracture after surgery and were divided into two groups: Among neck BMD changes (6 months minus 2 weeks after surgery) were calculated. Based on among neck BMD change, patients were classified into the BMD maintenance or improvement (change ≥ 0) and the BMD decrease groups (change < 0). Propensity score matching was performed to adjust for confounding factors. To predict the factors affecting neck BMD, hierarchical logistic regression analysis was performed. The dependent variable was the BMD maintenance or improvement group and the BMD decrease group. The independent variables were basic and medical information, and physical functions. RESULTS: The hierarchical logistic regression analysis results showed that movement control during one-leg standing affected femoral neck BMD independently from age, sex. The odds ratio for movement control during one-leg standing was 8.22. The discrimination rate of the model was 69.7%. CONCLUSION: This study suggested that adequate movement control during one-leg standing is important to maintain or improve neck BMD.

Association of muscle mass and quality with hand grip strength in elderly patients with heart failure.

In patients with heart failure, it is unknown whether the extracellular water (ECW)/intracellular water (ICW) ratio is associated with muscle strength, and thus, it is not well understood whether poor muscle quality contributes to muscular weakness. This study examined the relationship among hand grip strength, skeletal muscle mass index (SMI), and upper limb ECW/ICW ratio in patients with heart failure. This study followed a cross-sectional design. Demographic data, medical information, and hand grip strength were collected. The SMI and ECW/ICW ratio were measured using bio-impedance analysis (BIA). Hierarchical multiple regression analysis was conducted to identify factors associated with hand grip strength. 51 patients with heart failure were analyzed for this study (mean age 84.58 ± 7.18). Hierarchical multiple regression analysis identified SMI as well as upper limb ECW/ICW ratio as factors associated with hand grip strength, independent of age, sex, body mass index, and Life Space Assessment scores. Standardized partial regression coefficients representing the magnitude of involvement of each independent variable were 0.33 and - 0.16. The coefficient of determination adjusted for degrees of freedom (R2), representing the contribution rate of the regression equation, was 0.830. We revealed that loss of hand grip strength in patients with heart failure is associated with not only with a decrease in skeletal muscle mass, but also with a decline in muscle quality, characterized by an increased upper limb ECW/ICW ratio. BIA is a simple and useful method to measure the ECW/ICW ratio, and in turn, the muscle quality, in patients with heart failure.

Relationship Among 3 Different Core Stability Tests in Healthy Young Adults: Validity and Gender Differences.

CONTEXT: Core stability is important for preventing injury and improving performance. Although various tests for evaluating core stability have been reported to date, information on their relationship and the effect of gender differences is limited. This study aimed to (1) identify correlations among the 3 core stability tests and to examine the validity of each test and (2) identify gender differences in the test relationship and determine whether gender influenced test selection. DESIGN: Cross-sectional study. METHODS: Fifty-one healthy volunteers (27 men and 24 women) participated in the study. The participants underwent the following 3 tests: Sahrmann Core Stability Test (SCST), the lumbar spine motor control tests battery (MCBT), and Y Balance Test (YBT). Each parameter was analyzed according to all parameters and gender using the Spearman rank correlation coefficient. RESULTS: Overall, there was a strong positive correlation between SCST and MCBT and moderate positive correlations between SCST and YBT and between MCBT and YBT. Conversely, gender-specific analyses revealed no significant correlations between YBT and SCST and between YBT and MCBT in women, although significantly strong correlations were found among all tests in men. CONCLUSION: Although these 3 tests evaluated interrelated functions and may be valid as core stability tests, the results should be carefully interpreted when performing YBT in women.

Association between movement control during one-leg standing and femoral BMD in patients with hip fractures.

INTRODUCTION: Prior studies have focused only on the temporal component of one-leg standing, no reports have examined the relationship between the qualitative components of one-leg standing and femoral BMD. Thus, this study investigated whether quality (i.e., movement control) of one-leg standing also associated femoral BMD. MATERIALS AND METHODS: A total of 80 patients with unilateral hip fracture were included in a cross-sectional study. Basic and medical information and physical functions including movement control during one-leg standing were assessed at admission and 2 weeks after surgery, respectively. Hierarchical multiple regression analysis was performed to identify predictors of femoral BMDs on the non-fractured side. Dependent variables included femoral neck and total hip BMDs in models 1 and 2, respectively. RESULTS: Hierarchical multiple regression analysis (standardized partial regression coefficients) in model 1 identified age (- 0.18), sex (0.38), body mass index (BMI) (0.41), movement control during one-leg standing on the non-fractured side (0.19), and life-space assessment (0.17) as factors associating femoral neck BMD. Meanwhile, hierarchical multiple regression analysis (standardized partial regression coefficients) in model 2 identified age (- 0.12), sex (0.36), BMI (0.37), and movement control during one-leg standing on the non-fractured side (0.25) as factors associating total hip BMD. The coefficients of determination adjusted for degrees of freedom (R2) were 0.529 and 0.470 for models 1 and 2, respectively. CONCLUSION: Our results suggest that improving movement control during one-leg standing may be important for maintaining and improving femoral BMD on the non-fractured side.

Relationship Between Hip Frontal Dynamic Joint Stiffness and Frontal and Transverse Plane Hip Kinematics During Gait: Sex Differences.

CONTEXT: Previous studies have reported that the incidence of patellofemoral pain in women is 2.2 times higher than that in men. Lower hip frontal dynamic joint stiffness in women may be related to the magnitude of hip adduction and internal rotation associated with patellofemoral pain. OBJECTIVE: To identify sex differences in hip frontal dynamic joint stiffness and examine the relationship between hip frontal dynamic joint stiffness and hip adduction and internal rotation during gait. DESIGN: Cross-sectional study. SETTING: University campus. PARTICIPANTS: A total of 80 healthy volunteers (40 women and 40 men) participated in this study. INTERVENTION(S): Kinematic and kinetic data during gait were collected using a motion capture system and force plates. MAIN OUTCOME MEASURES: Hip frontal dynamic joint stiffness, hip adduction, and hip internal rotation were calculated during gait. RESULTS: Women demonstrated lower hip frontal dynamic joint stiffness than men during gait (P < .01). They also displayed decreased hip frontal dynamic joint stiffness associated with increased hip adduction (r = -.85, P < .001) and internal rotation (r = -.48, P < .001). Conversely, in men, decreased hip frontal dynamic joint stiffness was associated with increased hip adduction (r = -.74, P < .001) but not internal rotation (r = .17, P = .28). CONCLUSIONS: Sex differences between hip frontal dynamic joint stiffness and hip internal rotation during gait may contribute to the increased incidence of patellofemoral pain in women.

Effects of hypertonia on contracture development in rat spinal cord injury.

STUDY DESIGN: Experimental animal study. OBJECTIVES: Spastic hypertonia is originally believed to cause contractures from clinical observations. Botulinum toxin is effective for the treatment of spasticity and is widely used in patients who have joints with contractures. Using an established rat model with knee contractures after spinal cord injuries, we aimed to verify whether hypertonia contributes to contracture development, and the botulinum toxin improves structural changes in muscles and joint components responsible for contractures. SETTING: University laboratory in Japan. METHODS: To evaluate the effect of hypertonia on contracture development, the rats received botulinum toxin injections after spinal cord injuries. Knee extension motion was measured with a goniometer applying a standardized torque under anesthesia, and the contribution by muscle or non-muscle structures to contractures were calculated by measuring joint motion before and after the myotomies. We quantitatively measured the muscle atrophy, muscle fibrosis, and synovial intima length. RESULTS: Botulinum toxin injections significantly improved contractures, whereas did not completely prevent contracture development. Botulinum toxin was effective in improving the muscular factor, but little difference in the articular factor. Spinal cord injuries induced muscle atrophy, and botulinum toxin significantly accelerated muscle atrophy and fibrosis. The synovial intima length decreased significantly after spinal cord injuries, and botulinum toxin did not improve this shortening. CONCLUSIONS: This animal study provides new evidence that hypertonia is not the sole cause rather is the partial contributor of contractures after spinal cord injuries. Furthermore, botulinum toxin has adverse effects in the muscle.

Trunk lean gait decreases multi-segmental coordination in the vertical direction.

[Purpose] The strategy of trunk lean gait to reduce external knee adduction moment (KAM) may affect multi-segmental synergy control of center of mass (COM) displacement. Uncontrolled manifold (UCM) analysis is an evaluation index to understand motor variability. The purpose of this study was to investigate how motor variability is affected by using UCM analysis on adjustment of the trunk lean angle. [Subjects and Methods] Fifteen healthy young adults walked at their preferred speed under two conditions: normal and trunk lean gait. UCM analysis was performed with respect to the COM displacement during the stance phase. The KAM data were analyzed at the points of the first KAM peak during the stance phase. [Results] The KAM during trunk lean gait was smaller than during normal gait. Despite a greater segmental configuration variance with respect to mediolateral COM displacement during trunk lean gait, the synergy index was not significantly different between the two conditions. The synergy index with respect to vertical COM displacement during trunk lean gait was smaller than that during normal gait. [Conclusion] These results suggest that trunk lean gait is effective in reducing KAM; however, it may decrease multi-segmental movement coordination of COM control in the vertical direction.

Effects of exercise therapy on walking ability in individuals with knee osteoarthritis: a systematic review and meta-analysis of randomised controlled trials.

OBJECTIVE: To examine the effect of exercise therapy on the walking ability of individuals with knee osteoarthritis. DATA SOURCES: Randomised clinical trials (RCTs) were identified by searching through PubMed, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, and Cumulative Index to Nursing and Allied Health Literature. All literature published to October 2014 were included in the search. REVIEW METHODS: Data were collected from RCTs that compared the effects of exercise therapy on walking ability with the effects of no intervention or psychoeducational intervention in participants with knee osteoarthritis. The outcome data on the total distance walked (6-minute walk test); the amount of time spent walking (the time to walk arbitrary distances); and gait velocity were obtained and analysed. Standardized mean differences (SMDs) and 95% confidence intervals (CIs) were calculated. RESULTS: Twenty-eight RCTs were identified. Meta-analysis provided very-low-quality evidence that exercise therapy increased the total distance walked in the 6-minute walk test, in comparison with the effects of the control interventions (SMD = 0.44, 95% CI 0.27 to 0.60). Meta-analysis also provided low- or moderate-quality evidence that the amount of time spent walking and gait velocity were improved more by exercise therapy than by the control interventions (the amount of time spent walking: SMD = -0.50, 95% CI -0.70 to -0.30; gait velocity: SMD = 1.78, 95% CI 0.98 to 2.58). CONCLUSION: In individuals with knee osteoarthritis, exercise therapy can improve the amount of time spent walking, gait velocity, and maybe the total distance walked.

Cyclooxygenase-2 inhibitor celecoxib attenuates joint contracture following immobilization in rat knees.

BACKGROUND: The aim of this study is to clarify the following two points: First, whether a cyclooxygenase-2 mediated pathway is involved in the formation of immobilization-induced joint contracture and, second, the effectiveness of oral administration of non-steroidal anti-inflammatory drug celecoxib (CBX) for the prevention of myogenic and arthrogenic contracture following immobilization in a rat model. METHODS: Thirty male rats were randomly divided into three groups: immobilization (Im), Im + CBX, and control (n = 10 each). External fixation immobilized the right knee joint of Im and Im + CBX groups in flexion for 3 weeks. 50 mg/kg of CBX was administrated daily to the Im + CBX group during this period. The passive range of motion (ROM) of knee joints was measured before and after transection of knee flexor muscles and myogenic and arthrogenic ROM restrictions were calculated. The semitendinosus muscles and knee joints were investigated histologically to elucidate factors responsible for contracture. RESULTS: Myogenic ROM restrictions were exhibited both in Im and Im + CBX groups (44 ± 5 and 36 ± 8 °, respectively), but restrictions significantly decreased in the Im + CBX group compared to the Im group. Significant reductions of the muscle length ratios (Rt/Lt) and sarcomere number ratios (Rt/Lt) in knee flexor semitendinosus muscle, which are responsible for myogenic contracture, were also seen both in Im group (92 ± 5 and 92 ± 4 %, respectively) and Im + CBX group (97 ± 3 and 97 ± 3 %, respectively), but were inhibited by CBX administration (P < 0.05). Im and Im + CBX groups exhibited arthrogenic ROM restrictions with no significant differences (82 ± 3 and 83 ± 5 °, respectively). Posterior synovial length shortening and pathological changes (hemorrhage in joint cavities and capsule edema) in the knee joints were comparable between Im and Im + CBX groups. CONCLUSIONS: Oral administration of celecoxib partially reduced myogenic ROM restriction concomitantly with knee flexor muscle shortening following immobilization. These results imply that inflammation and nociception are involved in myogenic contracture formation independently of joint immobilization, and that CBX is effective in preventing joint contracture following immobilization in rats.

Biomechanical effects of lateral and medial wedge insoles on unilateral weight bearing.

[Purpose] Lateral wedge insoles reduce the peak external knee adduction moment and are advocated for patients with knee osteoarthritis. However, some patients demonstrate adverse biomechanical effects with treatment. In this study, we examined the immediate effects of lateral and medial wedge insoles under unilateral weight bearing. [Subjects and Methods] Thirty healthy young adults participated in this study. The subjects were assessed by using the foot posture index, and were divided into three groups: normal foot, pronated foot, and supinated foot groups. The knee adduction moment and knee-ground reaction force lever arm under the studied conditions were measured by using a three-dimensional motion capture system and force plates. [Results] In the normal and pronated groups, the change in knee adduction moment significantly decreased under the lateral wedge insole condition compared with the medial wedge insole condition. In the normal group, the change in the knee-ground reaction force lever arm also significantly decreased under the lateral wedge insole condition than under the medial wedge insole condition. [Conclusion] Lateral wedge insoles significantly reduced the knee adduction moment and knee-ground reaction force lever arm during unilateral weight bearing in subjects with normal feet, and the biomechanical effects varied according to individual foot alignment.

Does exercise therapy improve the health-related quality of life of people with knee osteoarthritis? A systematic review and meta-analysis of randomized controlled trials.

[Purpose] The aim of this study was to examine the effects of exercise therapy on the health-related QOL of people with knee osteoarthritis. [Subjects] Four databases (PubMed, Cochrane Central Register of Controlled Trials, the Physiotherapy Evidence Database, and the Cumulative Index to Nursing and Allied Health Literature) were searched for randomized controlled trials that evaluated the effects of exercise therapy on health-related QOL assessed by the SF-36 for inclusion in our systematic review. The methodological qualities of the trials were assessed independently by two reviewers using the PEDro scale. Pooled analyses with a random-effects model or a fixed-effects model were used in the meta-analyses to calculate the standardized mean differences and 95% confidence intervals. [Results] Twelve studies met the inclusion criteria. Our meta-analysis provides high-quality evidence that exercise therapy increases the summary score, physical functioning score, and role-physical score of knee osteoarthritis sufferers. Our meta-analysis also provides moderate-quality evidence that the physical component summary and mental component summary scores were improved to a greater extent by exercise therapy than by control interventions. [Conclusion] Exercise therapy can improve health-related QOL, as assessed by the SF-36, of knee osteoarthritis sufferers.

Effect of the Frequency and Duration of Land-based Therapeutic Exercise on Pain Relief for People with Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

[Purpose] This study aimed to investigate the influence of land-based exercise frequency and duration on pain relief for people with knee osteoarthritis (OA). [Subjects and Methods] The systematic review included randomized controlled trials that investigated this influence, which were identified by searches of PubMed, the Cochrane Central Register of Controlled Trials, the Physiotherapy Evidence Database, and the Cumulative Index to Nursing and Allied Health Literature. The exercise groups in the identified trials were categorized according to their type, frequency, and duration of exercise, and subgroup analyses were performed. [Results] Data integration of 17 studies (23 exercise groups) revealed a significant effect and a medium effect size. In subgroups involving strengthening exercise programs of ≥9 weeks duration, heterogeneity was found between subjects who performed up to 3 sessions/week and those who performed ≥4 sessions/week. In subgroups involving strengthening exercise programs of up to 3 sessions/week, there was heterogeneity between subjects who exercised for up to 8 weeks and those who exercised for ≥9 weeks. Heterogeneity was not confirmed in aerobic exercise subgroups. [Conclusion] Differences in exercise frequency and duration influence pain relief in effects of strengthening exercises but do not influence the effect size of aerobic exercise for people with knee OA.

Exploratory study of factors associated with probable respiratory sarcopenia in elderly subjects.

BACKGROUND: The diagnostic criteria for respiratory sarcopenia have been recently reported. However, no studies have clarified the characteristics of skeletal muscle impairment of the limbs in subjects with respiratory sarcopenia. This study aimed to explore the factors, including skeletal muscle, associated with probable respiratory sarcopenia in elderly subjects. METHODS: Subjects were classified into the probable respiratory sarcopenia group and nonrespiratory sarcopenia group. Probable respiratory sarcopenia was defined as the concurrent presence of respiratory muscle weakness (as less than the predicted value calculated from age, sex, and height) and low skeletal muscle mass (<7.0 kg/m2 in males and 5.7 kg/m2 in females). The following factors were measured: respiratory muscle strength, skeletal muscle mass index, muscle thickness and echo intensity of the rectus femoris, extracellular-to-intracellular water ratio, hand grip strength, 5 sit-to-stand, knee extension strength, bone mineral density, age, sex, body mass index, degree of frailty, presence or absence of medical history, presence or absence of habitual exercise, period of time since the start of exercise, and number of hours of exercise at a time. The association subjects with probable respiratory sarcopenia were analyzed using hierarchical logistic regression analysis. RESULTS: Twenty-six with probable respiratory sarcopenia and 54 with nonrespiratory sarcopenia were included. Hierarchical logistic regression analysis revealed that echo intensity was a significant predictor of probable respiratory sarcopenia. The odds ratio for echo intensity was 2.54 (95% confidence interval: 1.04-6.23). CONCLUSIONS: Our results suggest that a decrease in muscle quality in the lower extremity is associated with probable respiratory sarcopenia.

Evaluation of the relationship between truss/windlass mechanisms and foot stiffness while walking.

BACKGROUND: The truss/windlass coefficients ware reported as a surrogate parameter for foot stiffness while walking. However, the construct validity and reliability of whether the truss/windlass coefficients reflect foot stiffness have not been sufficiently validated. This study validated the truss/windlass coefficient reflects the construct validity and reliability of foot stiffness. METHODS: Participants were 25 healthy young males (21.6 ± 0.7 years). Foot stiffness was assessed using Simplified Foot Stiffness. It was determined by dividing the difference in foot load between sitting and standing by the rate of change in navicular height. The truss/windlass coefficient was calculated as the behavior of the foot arch during middle to late stance. To assess the reliability of each parameter, intraclass correlation coefficients (ICC 1.1) and Bland-Altman analysis were used, and Spearman's rank correlation coefficients were used to determine construct validity. RESULTS: The truss coefficient (ICC1.1 0.86) and Simplified Foot Stiffness (ICC1.1 0.87) demonstrated high reliability and no systematic error. However, the windlass coefficient (ICC1.1 0.73) demonstrated moderate reliability and proportional error. Furthermore, the truss coefficient had a significant positive correlation with Simplified Foot Stiffness (r = 0.504; p < 0.01), whereas the windlass coefficient did not (r = 0.06; p = 0.67). CONCLUSION: The truss coefficient was proposed as a highly reliable parameter that reflects foot stiffness. However, the windlass coefficient has a proportional error, despite being moderately reliable.

Sex differences in pelvis, thigh, and shank coordination during walking.

Differences in lower limb kinematics between males and females during functional activities may be attributed to sex differences in the incidence of patellofemoral pain, which is more common in females. To better comprehend the knee joint motion, it is necessary to understand both inter-segmental coordination patterns and angular amplitude. This exploratory study aimed to assess sex differences in pelvis-thigh and thigh-shank coordination patterns in the frontal and horizontal planes during walking. Data regarding the kinematic characteristics of the pelvis, thigh, and shank segments were collected from 26 males and 26 females performing walking at self-selected speeds using a 3D motion capture system. Furthermore, we compared the kinematics of the pelvis, thigh, and shank during walking as well as the pelvis-thigh and thigh-shank coordination patterns in the frontal and horizontal planes during the stance phase between males and females. Compared to males, females had greater thigh adduction (p < 0.001) and internal rotation (p < 0.001) throughout the stance phase; significantly greater frequency of the pelvis-thigh anti-phase pattern in the frontal plane in the early (p = 0.002) and mid-stance (p = 0.003); and significantly greater thigh-shank anti-phase pattern in the frontal plane in the early (p = 0.001) and mid-stance (p = 0.015). These results suggest the presence of sex differences in the inter-segmental coordination of the pelvis and lower limb during walking. However, as this study could not determine a causal relationship between female sex and knee joint injury, further longitudinal studies are needed to determine the effects of differences in coordination patterns on the pathophysiology of the injury and pain generation.

Association between physical function and parameters of hip structural analysis in patients with hip fracture.

OBJECTIVES: The current study sought to investigate whether physical function and activity were associated with hip structural analysis (HSA) parameters on the non-fracture side of patients with hip fractures. METHODS: Participants were patients with unilateral hip fracture treated by surgery. HSA of the proximal femur was conducted based on dual-energy x-ray absorptiometry data. HSA parameters in the narrow neck region included cross-sectional area (CSA), cross-sectional moment of inertia (CSMI), section modulus (SM), and buckling ratio (BR). Hierarchical multiple regression analysis was conducted to identify predictors of HSA. RESULTS: Except for the adjustment variables, age, gender and BMI, other variables were extracted. Hierarchical multiple regression analysis (standardised partial regression coefficients) identified movement control during one-leg standing on the non-fractured side (0.15) as factors associated with CSA. Hierarchical multiple regression analysis (standardised partial regression coefficients) identified hand grip (0.12, 0.23) as factors associated with CSMI and SM, respectively. Hierarchical multiple regression analysis (standardised partial regression coefficients) identified presence of steroid (0.23) and cerebrovascular disease (0.19) as factors associated with BR. The coefficients of determination adjusted for degrees of freedom (R2) were 0.545, 0.331, 0.401, and 0.148 for CSA, CSMI, SM, and BR, respectively. CONCLUSIONS: Our results indicate that movement control during 1-leg standing and muscle strength may be important for maintaining and improving bone strength.

Improvement of muscle quality assessed using the phase angle is influenced by recovery of knee extension strength in patients with hip fractures.

BACKGROUND AND AIMS: Studies reported that knee extension strength on the operated side in patients with hip fractures was not recovered to the level on the non-operated side 6 months after surgery or later. In a cross-sectional study, we revealed that a reduction in isometric knee extension muscle strength on the operated side in patients with hip fractures approximately 6 months after surgery was associated with not only a reduction in skeletal muscle mass but also a reduction in muscle quality, characterized by a reduction in the phase angle (PhA). Furthermore, the mechanisms of knee extension strength improvement can be clarified in more detail using the minimal significant change as the index of recovery. However, no longitudinal studies have examined the factors for knee extension strength improvement based on the minimal significant change in patients with hip fractures 6 months after surgery. This study aimed to longitudinally examine the factors influencing the recovery of knee extension strength based on the minimal significant change in patients with hip fractures between 2 weeks and approximately 6 months after surgery. METHODS: In this study, the outcomes used were basic and medical information, PhA, skeletal muscle index (SMI), pain, one-leg standing time, movement control during one-leg standing, and walking speed. For PhA, SMI, pain, one-leg standing time, movement control during one-leg standing, and walking speed, the amount of change was calculated by subtracting the data at 2 weeks from the data at 6 months. Group classification was determined by dividing the patients into two groups using a previous study as a reference: recovery group if the knee extension strength value approximately 6 months after surgery minus that 2 weeks after surgery was ≥3.3 kgf and non-recovery group if the value was <3.3 kgf. Logistic regression analysis was performed to explore the association between the recovery and non-recovery groups. RESULTS: The recovery group contained 55 patients, while the non-recovery group comprised 35 patients. The only significant factor associated with knee extension muscle strength in the recovery group was the amount of change in PhA. The odds ratio for the amount of change in PhA was 2.26. The discrimination rate of the model was 62.5%. CONCLUSIONS: Our results suggest that recovery of knee extension strength in patients with hip fractures after surgery was mainly because of improvements in muscle quality, not improvements in muscle mass or pain.