Sex-based differences and relationship with the restricted knee flexion angle due to aging: a comparative study.

BACKGROUND: The relationship between inferior patellar mobility (IPM) and knee flexion angle has yet to be elucidated. This study aimed to develop quantitative IPM measurement methods and clarify the relationship between IPM and knee flexion angle in community-dwelling older females. METHODS: This was a cross-sectional study. Overall, 128 healthy older women (age 65-79 years) were recruited from the community to evaluate the relationship between IPM and knee flexion angle. This study was performed between May 2015 and December 2017. The reference value of and sex differences in IPM were evaluated in 205 healthy young adults aged between 19 and 21 years. IPM was compared between healthy older and young women and was objectively measured using our specially designed patellofemoral arthrometer (PFA). Patellar mobility was calculated by normalization to body height. IPM reliability was assessed before all measurements. RESULTS: Intraclass correlation coefficients for intratester and intertester reliabilities varied from 0.87 to 0.99. The normal range based on two standard deviations of inferior patellar displacement/body height was 5.9-13.5% (young men), 5.1-14.3% (young women), and 1.2-8.8% (older women). IPM was significantly lower in older than young women (P < 0.001). There was a significant positive correlation (r = 0.72 and P < 0.01) between IPM and knee flexion angle in healthy older women unable to flex the knee joint fully. CONCLUSIONS: Our PFA has good intratester and intertester reliability. The results suggest that IPM decreases with aging in women. IPM and knee flexion angle are correlated among older women unable to flex the knee joint fully. CLINICAL TRIAL REGISTRATION: Not applicable.

The effects of endurance exercise combined with high-temperature head-out water immersion on serum concentration of brain-derived neurotrophic factor in healthy young men.

OBJECTIVES: To evaluate acute changes in serum brain-derived neurotrophic factor (BDNF) concentration following combined endurance exercise and heat stress through head-out water immersion (HOI). SETTING: Observational study with crossover design. METHODS: Ten healthy young male participants performed HOI at 40 °C (40 °C HOI) or continuous cycling at 60% of maximal oxygen uptake while immersed in 40 °C (40 °C HOI-ex) or 23 °C water (23 °C HOI-ex) for 15 min. Serum BDNF, cortisol and lactate concentrations, and core temperature (Tcore) were measured pre, immediately post, and 15 and 30 min post-immersion. RESULTS: BDNF concentration increased immediately and 15 min after 40 °C HOI-ex, but not after 40 °C or 23 °C HOI-ex. No changes in Tcore concentration were observed during 23 °C HOI-ex (Pre; 37.3 °C ± 0.3 °C, Post; 37.8 °C ± 0.2 °C, Post 15; 37.4 °C ± 0.3 °C, Post 30; 37.2 °C ± 0.2 °C). Tcore increased significantly post, post 15, and post 30 min of 40 °C HOI (Pre; 37.1 °C ± 0.4 °C, Post; 38.8 °C ± 0.5 °C, Post 15; 37.9 °C ± 0.4 °C, Post 30; 37.9 °C ± 0.2 °C) and 40 °C HOI-ex (Pre; 37.2 °C ± 0.2 °C, Post; 40.2 °C ± 0.7 °C, Post 15; 38.9 °C ± 0.5 °C, Post 30; 38.3 °C ± 0.5 °C). Tcore was higher in 40 °C HOI-ex compared with 40 °C HOI and 23 °C HOI-ex immediately post and post 15 min. Plasma lactate and cortisol were significantly higher in 40 °C HOI-ex compared with 40 °C HOI and 23 °C HOI-ex after immersion (p = 0.001). CONCLUSION: While 15 min HOI alone or thermoneutral exercise do not increase BDNF concentration, both combined may form a time-efficient strategy to acutely elevate BDNF.

Relationship Between Balance Recovery From a Forward Fall and Lower-Limb Rate of Torque Development.

The authors examined the relationship between the maximum recoverable lean angle via the tether-release method with early- or late-phase rate of torque development (RTD) and maximum torque of lower-limb muscle groups in 56 young healthy adults. Maximal isometric torque and RTD at the hip, knee, and ankle were recorded. The RTD at 50-ms intervals up to 250 ms from force onset was calculated. The results of a stepwise multiple regression analysis, early RTD for hip flexion, and knee flexion were chosen as predictive variables for the maximum recoverable lean angle. The present study suggests that some of the early RTD in the lower limb muscles, but not the maximum isometric torque, can predict the maximum recoverable lean angle.

Effect of ankle stretching combined with arm cycling on the improvement of calf muscle stiffness in patients with stroke: a pilot study.

[Purpose] This study aimed to ascertain whether ankle stretching combined with arm cycling compared with that without arm cycling results in greater improvement in maximum dorsiflexion range of motion (ROM), calf muscle stiffness, and gait velocity in the affected limb of patients with stroke. [Participants and Methods] Random ABAB reversal design was used in this study involving nine patients with stroke. Participants performed 10 min of ankle plantar flexor stretching through weight bearing using the tilt table under the following 2 conditions: with or without arm cycling at 60 revolutions per minute. Pre- and post-stretching maximum ROM and passive plantar flexion torque were measured using a custom-made passive torque indicator. Stiffness was calculated based on passive torque-angle relationships. [Results] Maximum ROM and stiffness significantly improved after stretching in both conditions, whereas no changes in gait velocity were found. The difference in pre- and post-stretching stiffness was significantly greater in the stretching with arm cycling group. Change in maximum ROM showed no difference between both stretching conditions. [Conclusion] This study indicates that ankle plantar flexor stretching combined with arm cycling was more effective than that without cycling in improving calf muscle stiffness in the affected limb of patients with stroke.

Custom-made hinged knee braces with extension support can improve dynamic balance.

Background/Objective: We investigated whether custom-made hinged knee braces can facilitate knee extensor and flexor strength and influence functional performance as compared with other knee braces. METHODS: We enrolled 28 healthy young participants with no history of physical activity or brace use. The participants executed functional performance tests under the following 5 conditions: 1) without a knee brace, 2) wearing a knee sleeve, 3) wearing a hinged knee brace without assistance, 4) wearing a knee brace with extension support (KBE), and 5) wearing a knee brace with flexion support (KBF). The KBE and KBF were custom-made hinged knee braces equipped with rubber tubes. The functional performance tests performed assessed maximal isokinetic strength, single-leg jumping height/distance, anterior and posterior reach distance on a single leg, and dynamic balance ability. RESULTS: The benefit of the custom-made hinged knee brace was observed only during the anterior reach distance on a single leg. The KBE allowed a significantly greater single-leg anterior reach distance when compared to that in the no brace condition. There was a significant relationship between the improvement in the single leg anterior reach distance with KBE and the changes in isokinetic knee extension with KBE compared to the no brace condition. With regard to other parameters, there were no differences compared with the use of other knee braces and thus no apparent benefit. CONCLUSION: Our findings suggest that using a KBE enhances performance during dynamic balance activity in individuals who benefit from improved knee extension strength.

Sex differences in passive lateral and medial patellar mobility in healthy young adults.

BACKGROUND: Sex differences in passive patellar mobility have not been quantitatively evaluated. OBJECTIVE: The present study aimed to: 1) investigate sex differences in absolute and normalized patellar mobility, and 2) verify the relationship between patellar mobility and knee joint laxity. METHODS: Two hundred and five pain-free individuals (205 knees, 103 men, 102 women) participated. Passive lateral and medial patellar displacement was measured using a modified patellofemoral arthrometer and manual pushing method at 0∘ and 30∘ knee flexion angles. The absolute values of lateral and medial patellar displacement (LPD and MPD, respectively), and values normalized to patellar width (PW) and body height (HT) were used in the final analysis. RESULTS: At a 30∘ knee flexion angle, LPD/PW and LPD/HT were greater in women than in men (LPD/PW: 27.0 ± 6.7% vs. 22.6 ± 6.7%, LPD/HT: 0.81 ± 0.19% vs. 0.70 ± 0.15%, respectively, P< 0.001, effect size > 0.50). Absolute and normalized lateral and medial patellar mobility correlated positively with the range of the knee extension angle. CONCLUSIONS: Sex differences in LPD/PW and LPD/HT at a 30∘ knee flexion were detected in healthy subjects. Although the knee extension angle related to both the lateral and medial direction of the patellar mobility, the relations were only fairly correlated in asymptomatic young subjects.

Age-related sex differences in erector spinae muscle endurance using surface electromyographic power spectral analysis in healthy humans.

BACKGROUND CONTEXT: Previous studies reported that the erector spinae muscle is more resistant to fatigue in healthy adult women than in men. However, no study has reported changes in back muscle fatigue with aging in healthy men and women. PURPOSE: The aim of this study was to evaluate age-related changes in muscle fatigue of erector spinae muscle in men and women. STUDY DESIGN/SETTING: This cross-sectional study was conducted in a laboratory. PATIENT SAMPLE: Fifty-three healthy subjects (11 elderly men, 11 elderly women, 17 young men, and 14 young women) without low back pain history. OUTCOME MEASURES: The median frequency (MF) and mean power frequency (MPF) during trunk holding test were derived from the raw electromyographic (EMG) signal using Fast Fourier Transform spectrum analysis program. The rates of changes in MF and MPF were calculated. METHODS: Subjects performed the unsupported trunk holding test until exhaustion. The results of power spectral analysis of the EMG activity of the left erector spinae muscle were compared in both age groups and sexes. RESULTS: The endurance time in young men was significantly shorter than in young women. The slopes of MF and MPF in young men were significantly higher than in young women. There were no significant differences in MF and MPF slopes of elderly men and elderly women. Furthermore, the MF and MPF slopes were significantly lower in elderly men than young men but similar in the two women groups. CONCLUSIONS: Age-related changes in the slopes of MF and MPF of erector spinae muscle occur in healthy men but not in healthy women.