Leg Extension Power Research Articles

Effects of muscle quantity, muscle quality, and phase angle on whole-body reaction time in 5164 adults aged 20-91years.

Muscle quantity, defined as appendicular lean mass (ALM); muscle quality, defined as the ratio of muscle strength to ALM; and bioelectrical impedance analysis (BIA)-derived phase angle (PhA) are determinants of physical performance. We examined whether muscle quality indices were significant predictors of the whole-body reaction time (WBRT) in healthy female and male adults aged 20-91years. Data from 5164 adults (2869 women and 2295 men; mean age ± standard deviation, 60.9 ± 15.6years) were analyzed. Height and weight were measured, and body mass index was calculated. ALM was estimated using a previously validated 8-electrode multi-frequency BIA. PhA was measured at 50kHz using a BIA device. Knee extension strength (KES), leg extension power (LEP), and flexibility were examined. The ALM to weight (ALM/weight), KES to ALM (KES/ALM), and LEP to KES (LEP/KES) ratios were calculated. In the WBRT test, participants were asked to stand on a force plate and jump upright as quickly as possible in response to a light stimulus. The WBRT was divided into the response initiation and motion execution phases. ALM/weight, KES/ALM, LEP/KES, PhA, and flexibility were significant independent predictors of WBRT and the time of the motion execution phase (p < 0.001). However, PhA was not a significant predictor of the time of response initiation phase. Muscle quantity (ALM/weight), muscle quality (KES/ALM and LEP/KES), PhA, and flexibility are determinants of WBRT test performance, particularly in the motion execution phase.

Association of skeletal muscle function, quantity, and quality with gut microbiota in Japanese adults: A cross-sectional study.

The gut microbiota has emerged as a new intervention target for sarcopenia. Prior studies in humans have focused on the association between gut microbiota and skeletal muscle quantity, while the evidence on muscle function and quality is lacking. This study aimed to identify gut microbiota genera associated with skeletal muscle function, quantity, and quality in a general population of Japanese adults. This cross-sectional study included 164 participants aged 35-80 years, women and men recruited from urban areas of Japan. Fecal samples were collected and analyzed using 16S rRNA gene amplicon sequencing. Skeletal muscle function was measured using handgrip strength and leg extension power (LEP), while skeletal muscle mass was estimated using bioelectrical impedance analysis. Phase angle was used as a measure of skeletal muscle quality. Multivariate linear regression analysis stratified by age group was used to examine the association between the dominant genera of the gut microbiota and skeletal muscle variables. A significant association was found between Bacteroides and Prevotella 9 with LEP only in the ≥60 years group. When both Bacteroides and Prevotella 9 were included in the same regression model, only Bacteroides remained consistently and significantly associated with LEP. No significant associations were observed between skeletal muscle mass, handgrip strength, and phase angle and major gut microbiota genera. In this study, we observed a significant positive association between Bacteroides and leg muscle function in older adults. Further studies are required to elucidate the underlying mechanisms linking Bacteroides to lower-extremity muscle function. Geriatr Gerontol Int 2024; 24: 53-60.

The relationship between visual function and physical performance in the Study of Muscle, Mobility and Aging (SOMMA).

The relationship of types of visual function to different aspects of physical function, especially strength and coordination, has been understudied, but delineation of these relationships could suggest potentially modifiable targets prior to the onset of disability. Cross-sectional analysis of visual function (self-reported eyesight and eye disease, visual acuity, contrast sensitivity) and physical function tests in 877 older adults (mean age 76.36±5.01 years, 59.2% women, and 13.3% Black race). Separate linear regression models were constructed for short physical performance battery (SPPB), expanded SPPB (eSPPB), their components (gait speed, chair stand, balance, narrow walk), stair climb, four-square step, leg extension peak power and strength, and grip strength. In adjusted models, worse acuity, worse contrast sensitivity, and self-reported poor vision were significantly associated with worse performance on the eSPPB and four-square step test. Worse contrast sensitivity, but not acuity, was significantly associated with shorter balance times, slower chair stand pace, longer stair climb time, and worse SPPB score. Associations of worse acuity and contrast sensitivity with weaker leg extension power, leg strength, and grip strength were attenuated by covariate adjustment. Self-reported macular degeneration, but not cataract or glaucoma, was associated with worse performance on SPPB, eSPPB, balance, stair climb, and four-square step tests in adjusted models. Worse contrast sensitivity and macular degeneration remained associated with worse SPPB and balance after controlling for visual acuity and self-reported eyesight. Poor contrast sensitivity was more strongly associated with worse physical performance than acuity, especially for complex tasks that dynamically challenge coordination and balance. Future studies should examine if older adults with contrast sensitivity impairment would benefit from targeted intervention to decrease their risk of disability.

Mitochondrial Energetics in Skeletal Muscle Are Associated With Leg Power and Cardiorespiratory Fitness in the Study of Muscle, Mobility and Aging.

Mitochondrial energetics are an important property of aging muscle, as generation of energy is pivotal to the execution of muscle contraction. However, its association with functional outcomes, including leg power and cardiorespiratory fitness, is largely understudied. In the Study of Muscle, Mobility, and Aging, we collected vastus lateralis biopsies from older adults (n = 879, 70-94 years, 59.2% women). Maximal State 3 respiration (Max OXPHOS) was assessed in permeabilized fiber bundles by high-resolution respirometry. Capacity for maximal adenosine triphosphate production (ATPmax) was measured in vivo by 31P magnetic resonance spectroscopy. Leg extension power was measured with a Keiser press system, and VO2 peak was determined using a standardized cardiopulmonary exercise test. Gender-stratified multivariate linear regression models were adjusted for age, race, technician/site, adiposity, and physical activity with beta coefficients expressed per 1-SD increment in the independent variable. Max OXPHOS was associated with leg power for both women (β = 0.12 Watts/kg, p < .001) and men (β = 0.11 Watts/kg, p < .050). ATPmax was associated with leg power for men (β = 0.09 Watts/kg, p < .05) but was not significant for women (β = 0.03 Watts/kg, p = .11). Max OXPHOS and ATPmax were associated with VO2 peak in women and men (Max OXPHOS, β women = 1.03 mL/kg/min, β men = 1.32 mL/kg/min; ATPmax β women = 0.87 mL/kg/min, β men = 1.50 mL/kg/min; all p < .001). Higher muscle mitochondrial energetics measures were associated with both better cardiorespiratory fitness and greater leg power in older adults. Muscle mitochondrial energetics explained a greater degree of variance in VO2 peak compared to leg power.

The relationship between muscle power, functional performance, accelerometer-based measurement of physical activity and patient-reported outcomes in patients with hip osteoarthritis: A cross-sectional study

BackgroundPatients with unilateral hip osteoarthritis appear to have between-leg differences in leg extension power (LEP). The Nottingham Leg Extensor Power Rig provides reliable and valid results but requires sensitive equipment. It would be relevant to identify measures closely associated with this test. Objective(i) To investigate if LEP is lower in the affected leg compared to the non-affected leg. Furthermore, to investigate the associations between LEP and the measures: (ii) Functional performance, (iii) accelerometer-based measurement of physical activity and (iv) patient-reported outcome measures (PROM). DesignCross-sectional study including 60 patients (30 men, 30 women) with hip osteoarthritis scheduled for hip replacement. MethodThe counter movement jump and 10-m sprint tests were used to determine functional performance, accelerometer-sensors were used to determine physical activity and the Copenhagen Hip and Groin Outcome Score (HAGOS) was used to determine PROM. Results(i) LEP in the affected leg corresponded to 79% [95% CI 74%; 85%] of the non-affected leg, (ii) LEP was positively associated with functional performance tests (β 0.63 to 0.78, p < 0.05), (iii) positively associated although non-significantly with physical activity (β 0.16 to 0.23, p > 0.05) and (iv) positively associated with the six HAGOS subscales (β 0.25 to 0.54, p < 0.05). ConclusionFunctional performance tests may be used as feasible, inexpensive and fast ways to assess LEP in clinical settings. These results may suggest that interventions aimed at improving LEP can improve functional performance and PROM, but not physical activity. Future research is needed to confirm the causality of these cross-sectional findings. The clinical trial registration numbersDanish Data Protection Agency (1-16-02-640-14), ClinicalTrials.gov (NTC02301182) and approved by the Danish Biomedical Research Ethics Committee (1-10-72- 343-14) prior to data collection.

Association between elastography-assessed muscle mechanical properties and high-speed dynamic performance

Clarifying the muscular factors that contribute to performance improvement can be beneficial for athletes and coaches. The present study examined the relationships between the resting muscle shear modulus and dynamic performance during the stretch-shortening cycle (SSC) and explosive exercises. To this end, we measured the jump height during three types of vertical jumps (squat jump [SJ], countermovement jump [CMJ], and rebound jump [RJ]) and the multi-joint leg extension power at three velocities (low, moderate, and high) of 30 healthy women. Using ultrasound elastography, the resting shear modulus of the vastus lateralis was assessed in the sitting position as an index of passive muscle mechanical properties. The results showed that the shear modulus was positively correlated with RJ height and multi-joint leg extension power at moderate and high velocities (r = 0.435–0.563, P < 0.05). There was no significant correlation between the shear modulus and SJ height, CMJ height, and multi-joint leg extension power at low velocity. Contact time (i.e., the time under force exertion against the ground) during RJ (161 ± 19 ms) was 19% of that during CMJ (869 ± 171 ms). The results suggest that passive muscle mechanical properties play an important role in high-speed SSCs and dynamic explosive performance.

Lower Limb Extension Power is Associated With Slope Walking Joint Loading Mechanics in Older Adults.

Fall-related injuries are associated with muscle weakness and common during slope walking in older adults. However, no study has evaluated the relationship between muscle weakness, measured by maximal lower limb extension power, and older adults' ability to navigate slope walking for a better understanding of fall prevention. Therefore, the purpose of this study was to investigate the association between maximal lower limb extension power and joint mechanics during slope walking. Fifteen healthy older adults were tested. Lower limb extension power was measured using the Leg Extension Power Rig. Kinematic and kinetic analysis was performed during level (0°), incline (10°), and decline (10°) slope walking. Greater maximal lower limb extension power was significantly (p < .050; Cohen's f2 > 0.35) associated with multiple kinetic and kinematic joint mechanic variables across stance phase of the gait cycle during level, incline, and decline walking. These findings will allow clinicians to better educate patients and develop interventions focused on fall prevention and improving functional mobility in older adults.

The combination of cardiorespiratory fitness and muscular fitness, and prevalence of diabetes mellitus in middle-aged and older men: WASEDA\u2019S Health Study

BackgroundAlthough the negative relationship between cardiorespiratory fitness (CRF) or muscular fitness and diabetes mellitus were respectively observed in many previous studies, there is still a lack of studies that include CRF and muscular fitness simultaneously. Therefore, this study aimed to investigate the relationship between the combination of CRF and muscular fitness and diabetes through a cross-sectional study. MethodsThis study was part of WASEDA'S Health Study, a cohort study launched in 2014. We used a part of the baseline data collected for this study. Maximal exercise test using a cycle ergometer and leg extension power (LEP) test were respectively used to evaluate CRF and muscular fitness. Since LEP is affected by body weight, relative LEP (rLEP) which is LEP per body weight, was used as an index of muscular fitness. 796 men (56.5 ± 10.4 years old) who completed a medical examination and fitness tests, were divided into two groups based on CRF and rLEP, respectively. The prevalence of diabetes was collected based on a self-reported questionnaire or blood test. Odds ratios and 95% confidence intervals (CIs) for the prevalence of diabetes were obtained using logistic regression models while adjusting for age, body mass index, exercise habits, family history of diabetes, smoking habits, and drinking habits.Results55 (7%) participants had diabetes. Compared to participants with lower CRF or rLEP, the odds ratio (95% CIs) of diabetes in those with higher CRF or rLEP was 0.46 (0.21–0.98) or 0.34 (0.16–0.74), respectively. Furthermore, using the lower CRF and lower rLEP group as the reference, the odds ratio (95% CIs) for the lower CRF and higher rLEP group was 0.32 (0.12–0.88), and higher CRF and higher rLEP group was 0.21 (0.07–0.63), after adjusting for potential confounding factors.ConclusionsCRF and rLEP have independent and joint inverse associations with diabetes prevalence. In addition, participants with high CRF and high rLEP had a lower prevalence of diabetes compared to those with only high CRF or only high rLEP.

Determinants of whole-body maximal aerobic performance in young male and female athletes: The roles of lower extremity muscle size, strength and power.

This study sought to determine whether lower extremity muscle size, power and strength could be a determinant of whole-body maximal aerobic performance in athletes. 20 male and 19 female young athletes (18 ± 4 years) from various sporting disciplines participated in this study. All athletes performed a continuous ramp-incremental cycling to exhaustion for the determination of peak oxygen uptake (: the highest over a 15-s period) and maximal power output (MPO: power output corresponding to ). Axial scanning of the right leg was performed with magnetic resonance imaging, and anatomical cross-sectional areas (CSAs) of quadriceps femoris (QF) and hamstring muscles at 50% of thigh length were measured. Moreover, bilateral leg extension power and unilateral isometric knee extension and flexion torque were determined. All variables were normalised to body mass, and six independent variables (, CSAs of thigh muscles, leg extension power and knee extension and flexion torque) were entered into a forward stepwise multiple regression model with MPO being dependent variable for males and females separately. In the males, was chosen as the single predictor of MPO explaining 78% of the variance. In the females, MPO was attributed to, in the order of importance, (p < 0.001) and the CSA of QF (p = 0.011) accounting for 84% of the variance. This study suggests that while oxygen transport capacity is the main determinant of MPO regardless of sex, thigh muscle size also has a role in whole-body maximal aerobic performance in female athletes.

30s sit-to-stand power is positively associated with chest muscle thickness in COVID-19 survivors.

IntroductionAfter hospitalization, early detection of musculoskeletal sequelae might help healthcare professionals to improve and individualize treatment, accelerating recovery after COVID-19. The objective was to determine the association between the 30s sit-to-stand muscle power (30s-STS) and cross-sectional area of the chest muscles (pectoralis) in COVID-19 survivors.MethodThis cross-sectional study collected routine data from COVID-19 survivors one month after hospitalization: 1) a chest computed tomography (CT) scan and 2) a functional capacity test (30s-STS). The pectoralis muscle area (PMA) was measured from axial CT images. For each gender, patients were categorized into tertiles based on PMA. The 30s-STS was performed to determine the leg extension power. The allometric and relative STS power were calculated as absolute 30s-STS power normalized to height squared and body mass. The two-way ANOVA was used to compare the gender-stratified tertiles of 30s-STS power variants.ResultsFifty-eight COVID-19 survivors were included (mean age 61.2 ± 12.9 years, 30/28 (51.7%/48.3%) men/women). The two-way ANOVA showed significant differences between the PMA tertiles in absolute STS power (p = .002) and allometric STS power (p = .001). There were no significant gender x PMA tertile interactions (all variables p > .05). The high tertile of PMA showed a higher allometric STS power compared to the low and middle tertile, p = .002 and p = .004, respectively. Absolute STS power and allometric STS power had a moderate correlation with the PMA, r = 0.519 (p < .001) and r = 0.458 (p < .001) respectively.ConclusionThe 30s-STS power is associated with pectoralis muscle thickness in both male and female COVID-19 survivors. Thus, this test may indicate global muscle-wasting and may be used as a screening tool for lower extremity functional capacity in the early stages of rehabilitation planning in COVID-19 survivors.

Muscle function following testosterone replacement in men on opioid therapy for chronic non-cancer pain: A randomized controlled trial.

Chronic pain and opioid treatment are associated with increased risk of male hypogonadism and subsequently decreased muscle function. A diagnosis of hypogonadism is based on the presence of low total testosterone and associated symptoms. The effect of testosterone replacement therapy on muscle function in men with chronic pain and low total testosterone remains to be investigated. To investigate the effects of testosterone replacement therapy on muscle function and gait performance in men treated with opioids for chronic non-cancer pain. A double-blind, placebo-controlled study. Forty-one men (>18 years) with opioid-treated chronic pain and serum total testosterone <12nmol/L were randomized to 24weeks testosterone replacement therapy (testosterone undecanoate injection three times/6 months, n =20) or placebo injections (n =21). Muscle function was measured as leg press maximal voluntary contraction, leg extension power using the Nottingham power rig and handgrip strength using a handheld dynameter. Gait performance was measured at usual and maximal gait speed on a 10-m track. Body composition (lean body mass and fat mass) was determined by dual-energy X-ray absorptiometry. Mann-Whitney tests were performed on ∆-values (24-0weeks) between testosterone replacement therapy and placebo. At baseline, median (interquartile range) age was 55 ± 13 years and BMI was 30.7 ± 5.2kg/m2 . ∆-muscle function and ∆-gait performance were similar between testosterone replacement therapy and placebo. Median ∆-leg press maximal voluntary contraction was 174.2 ± 406.7 Newton, following testosterone replacement therapy, and 7.6 ± 419.1 Newton, after placebo, p=0.091. ∆-lean body mass was significantly higher following testosterone replacement therapy compared to placebo, 3.6 ± 2.7versus 0.1 ± 3.5kg, respectively (p<0.001). Testosterone replacement therapy, compared to placebo, did not improve muscle function or gait performance despite increased lean body mass. Changes in body composition did not infer any changes in muscle function. 24weeks testosterone replacement therapy in opioid-treated men with pain-related male hypogonadism did not improve muscle function.

Changes in systemic GDF15 across the adult lifespan and their impact on maximal muscle power: the Copenhagen Sarcopenia Study

BackgroundAlthough growth differentiation factor 15 (GDF15) is known to increase with disease and is associated with low physical performance, the role of GDF15 in normal ageing is still not fully understood. Specifically, the influence of circulating GDF15 on impairments in maximal muscle power (a major contributor to functional limitations) and the underlying components has not been investigated.MethodsData from 1305 healthy women and men aged 20 to 93 years from The Copenhagen Sarcopenia Study were analysed. Circulating levels of GDF15 and markers of inflammation (tumor necrosis factor‐alpha, interleukin‐6, and high‐sensitivity C‐reactive protein) were measured by ELISA (R&D Systems) and multiplex bead‐based immunoassays (Bio‐Rad). Relative (normalized to body mass), allometric (normalized to height squared), and specific (normalized to leg muscle mass) muscle power were assessed by the Nottingham power rig [leg extension power (LEP)] and the 30 s sit‐to‐stand (STS) muscle power test. Total body fat, visceral fat, and leg lean mass were assessed by dual energy X‐ray absorptiometry. Leg skeletal muscle index was measured as leg lean mass normalized to body height squared.ResultsSystemic levels of GDF15 increased progressively as a function of age in women (1.1 ± 0.4 pg·mL−1·year−1) and men (3.3 ± 0.6 pg·mL−1·year−1) (both P < 0.05). Notably, GDF15 increased at a faster rate from the age of 65 years in women (11.5 ± 1.2 pg·mL−1·year−1, P < 0.05) and 70 years in men (19.3 ± 2.3 pg·mL−1·year−1, P < 0.05), resulting in higher GDF15 levels in men compared with women above the age of 65 years (P < 0.05). Independently of age and circulatory markers of inflammation, GDF15 was negatively correlated to relative STS power (P < 0.05) but not LEP, in both women and men. These findings were mainly explained by negative associations of GDF15 with specific STS power in women and men (both P < 0.05).ConclusionsA J‐shaped relationship between age and systemic GDF15 was observed, with men at older age showing steeper increases and elevated GDF15 levels compared with women. Importantly, circulating GDF15 was independently and negatively associated with relative STS power, supporting the potential role of GDF15 as a sensitive biomarker of frailty in older people.

The Associations of Handgrip Strength and Leg Extension Power Asymmetry on Incident Recurrent Falls and Fractures in Older Men.

Evaluating asymmetries in muscle function could provide important insights for fall risk assessments. We sought to determine the associations of (i) handgrip strength (HGS) asymmetry and (ii) leg extension power (LEP) asymmetry on risk of incident recurrent falls and fractures in older men. There were 5 730 men with HGS asymmetry data and 5 347 men with LEP asymmetry data from the Osteoporotic Fractures in Men (MrOS) study. A handgrip dynamometer measured HGS and a Nottingham Power Rig ascertained LEP. Percent difference in maximal HGS between hands was calculated, and asymmetric HGS was defined as men in the highest quartile of dissimilarity for HGS between hands. The same approach was used to determine asymmetric LEP. Participants self-reported falls every 4 months after the baseline exam, and persons with ≥2 falls in the first year were considered recurrent fallers. Fractures and their dates of occurrence were self-reported and confirmed with radiographic reports. Older men in the highest HGS asymmetry quartile had a 1.20 (95% confidence interval [CI]: 1.01-1.43) relative risk for incident recurrent falls. Likewise, men in the highest HGS asymmetry quartile had a higher risk for incident fractures: 1.41 (CI: 1.02-1.96) for hip, 1.28 (CI: 1.04-1.58) for major osteoporotic, and 1.24 (CI: 1.06-1.45) for nonspine. There were no significant associations between LEP asymmetry and recurrent falls or fractures. Asymmetric HGS could be a novel risk factor for falls and fractures that is more feasible to measure than LEP. Fall risk assessments should consider evaluating muscle function, including HGS asymmetry.

Detraining Effects on Musculoskeletal Parameters in Early Postmenopausal Osteopenic Women: 3-Month Follow-Up of the Randomized Controlled ACTLIFE Study

Periods of absence from supervised group exercise while maintaining physical activity might be a frequent pattern in adults' exercise habits. The aim of the present study was to determine detraining effects on musculoskeletal outcomes after a 3-month detraining period in early post-menopausal, osteopenic women. Due to the COVID-19 pandemic, we terminated the 18-month randomized controlled ACTLIFE exercise intervention immediately after the 13-month follow-up assessment. This put an abrupt stop to the high-intensity aerobic and resistance group exercise sessions undertaken three times per week by the exercise group (EG: n = 27) and the gentle exercise program performed once per week for the attention control group (CG: n = 27); but both groups were permitted to conduct individual outdoor activity for the 3-month lock-down period. Study endpoints were lean body mass (LBM), bone mineral density (BMD) at the lumbar spine (LS), maximum hip-/leg extension strength and power. Detraining-induced reductions of LBM, hip/leg strength and power (but not BMD-LS) were significantly greater (p < 0.001 to p = 0.044) compared with the CG. Significant exercise effects, i.e. differences between EG and CG, present after 13 months of exercise, were lost after 3 months of detraining for LBM (p = 0.157) and BMD-LS (p = 0.065), but not for strength (p < 0.001) and power (p < 0.001). Of note, self-reported individual outdoor activities and exercise increased by about 40% in both groups during the lock-down period. Three months' absence from a supervised group exercise protocol resulted in considerable detraining effects for musculoskeletal parameters. Thus, exercise programs for adults should be continuous rather than intermittent.Trial registration number: ClinicalTrials.gov: NCT04420806, 06.05.2020.

Determinants of Resting Oxidative Stress in Middle-Aged and Elderly Men and Women: WASEDA'S Health Study.

Previous studies have not investigated the determinants of resting oxidative stress, including physical fitness, as it relates to redox regulation. The present study therefore was aimed at identifying lifestyle and biological factors that determine resting oxidative stress, including objectively measured physical fitness. In 873 middle-aged and elderly men and women, age and anthropometric parameters, lifestyle-related parameters, medication and supplementation status, physical fitness, biochemical parameters, and nutritional intake status, as well as three plasma oxidative stress markers: protein carbonyl (PC), F2-isoprostane (F2-IsoP), and thiobarbituric acid reactive substances (TBARS), were surveyed and measured. The determinants of PC, F2-IsoP, and TBARS in all participants were investigated using stepwise multiple regression analysis. In PC, age (β = −0.11, P = 0.002), leg extension power (β = −0.12, P = 0.008), BMI (β = 0.12, P = 0.004), and HDL-C (β = 0.08, P = 0.040) were included in the regression model (adjusted R2 = 0.018). In the F2-IsoP, smoking status (β = 0.07, P = 0.060), BMI (β = 0.07, P = 0.054), and HbA1c (β = −0.06, P = 0.089) were included in the regression model (adjusted R2 = 0.006). In TBARS, glucose (β = 0.18, P < 0.001), CRF (β = 0.16, P < 0.001), age (β = 0.15, P < 0.001), TG (β = 0.11, P = 0.001), antioxidant supplementation (β = 0.10, P = 0.002), and HbA1c (β = −0.13, P = 0.004) were included in the regression model (adjusted R2 = 0.071). In conclusion, the present study showed that age, anthropometric index, lifestyle-related parameters, medication and supplementation status, objectively measured physical fitness, biochemical parameters, and nutritional intake status explain less than 10% of oxidative stress at rest.

Myosin heavy chain expression relationships to power-load and velocity-load curves

Velocity- and power-based training are popular methods of determining training session loads and volumes. One factor that may influence load-velocity and load-power properties of an individual is the myosin heavy chain (MHC) composition of the muscle. The aim of this study was to examine the relationship between MHC composition and both load-velocity and load-power properties of muscle performance. Forty-two men with a variety of training backgrounds took part in this study (mean±SD; age=22.4±3.5 yrs, hgt=1.78±0.07 m, BW=78.7±13.3 kg). After testing leg extension one repetition maximum (1 RM), subjects performed maximal effort leg extensions at loads from 30% to 90% 1 RM. Muscle biopsies from the vastus lateralis were analyzed via SDS-PAGE electrophoresis technique for MHC content (IIx=13.8±12.9%, IIa=49.4±10.3%, I=36.8±11.3%). Leg extension rotational velocity and power were plotted against relative loads for all subjects. Significant correlations (P<0.05) were observed for MHC IIa with all performance variables (i.e. slopes, intercepts, peaks and relative loads). Relationships indicated that greater %MHC IIa was associated with greater velocity intercepts, more negative load-velocity slopes, greater maximal power, and with maximal power occurring at a lower relative intensity (% 1 RM). These data indicate that muscle velocity and power characteristics appear to be partially influenced by MHC content in a manner consistent with single muscle fiber contractile properties.

Muscle Function Tests as Supportive Outcome Measures for Performance-Based and Self-Reported Physical Function in Patients With Knee Osteoarthritis: Exploratory Analysis of Baseline Data From a Randomized Trial.

Holm, PM, Kemnitz, J, Bandholm, T, Wernbom, M, Schrøder, HM, and Skou, ST. Muscle function tests as supportive outcome measures for performance-based and self-reported physical function in patients with knee osteoarthritis: Exploratory analysis of baseline data from a randomized trial. J Strength Cond Res 36(9): 2635-2642, 2022-Uncertainty on the role of muscle function in relation to physical function in knee osteoarthritis (KOA) persists. This study aimed to assess the associations between muscle function and performance-based and self-reported physical function in patients with KOA. Physical function in 80 subjects with symptomatic and radiographic KOA was assessed using 40-m fast-paced walk, 30-second chair stand, 9-step stair climb tests, and the subscale activities of daily living from the Knee injury and Osteoarthritis Outcome Score (KOOS-ADL). Measurements of muscle function included leg extension (LE) power, knee extension (KE) torque, and estimated leg press one repetition maximum (LP RM). Associations were investigated using multivariable hierarchical linear regressions adjusted for age, sex, body mass index, self-reported physical activity, and thigh muscle lean area. Leg extension power was significantly associated with 40-m walk, stair climb, and 30-second chair stand, explaining 18, 8, and 3% of additional variance, respectively. Knee extension torque explained 13, 7, 17, and 7% of additional variance in the 40-m walk, stair climb, 30-second chair stand, and KOOS-ADL, respectively. Leg press one repetition maximum explained 11% of additional variance in the 30-second chair stand. In conclusion, LE power was the best explanatory variable for performance on the 40-m walk and stair climb tests, whereas KE torque best explained chair stand performance. Only KE torque was associated with KOOS-ADL. Our results highlight the importance of selecting supportive muscle function tests based on the specific physical function and suggest that other factors may be more important for certain physical function outcomes. Level of significance p < 0.05. Trial identifier: NCT03215602.

Relation between leg extension power and 30-s sit-to-stand muscle power in older adults: validation and translation to functional performance

This study aimed to assess the validity and functional relevance of a standardized procedure to assess lower limb muscle power by means of the 30-s sit-to-stand (STS) test when compared to leg extension power (LEP), traditional STS performance and handgrip strength. A total of 628 community-dwelling older subjects (60–93 years) from the Copenhagen Sarcopenia Study were included. Physical performance was assessed by the 30-s STS and 10-m maximal gait speed tests. Handgrip strength and LEP were recorded by a hand-held dynamometer and the Nottingham power rig, respectively. STS muscle power was calculated using the subjects’ body mass and height, chair height and the number of repetitions completed in the 30-s STS test. We found a small albeit significant difference between LEP and unilateral STS power in older men (245.5 ± 88.8 vs. 223.4 ± 81.4 W; ES = 0.26; p < 0.05), but not in older women (135.9 ± 51.9 vs. 138.5 ± 49.6 W; ES = 0.05; p > 0.05). Notably, a large positive correlation was observed between both measures (r = 0.75; p < 0.001). Relative STS power was more strongly related with maximal gait speed than handgrip strength, repetition-based STS performance and relative LEP after adjusting for age (r = 0.53 vs 0.35–0.45; p < 0.05). In conclusion, STS power obtained from the 30-s STS test appeared to provide a valid measure of bilateral lower limb power and was more strongly related with physical performance than maximal handgrip strength, repetition-based STS performance and LEP.

WITHDRAWN: Effects of progressive resistance training for early postoperative fast-track total hip or knee arthroplasty: A systematic review and meta-analysis

Abstract Introduction Progressive resistance training (PRT) is one of the most commonly used exercise methods after joint replacement, while its effectiveness and safety are still controversial. Therefore, it`s vital to investigate the effect of PRT on muscle strength and functional capacity early postoperative total hip arthroplasty (THA) or total knee arthroplasty (TKA). Method Relevant studies were identified via a search of Medline, Web of science and Cochrane Library from 2002 to 12 May 2020. A meta-analysis was performed to compare postoperative outcomes between PRT and standard rehabilitation (SR) with respect to muscle strength measurement, functional recovery evaluation, and incidence of adverse events. Results fifteen of 704 studies which comprised 7 THAs and 8 TKAs, involving 1,021 adult patients were eligible for inclusion in the meta-analysis. There were no significant differences between the two groups after TKA in the 6-WMT (95% CI= -31.03, -28.70), SCP (95% CI= -1.57, 0.45), Leg extension power (95% CI= -0.06, 0.08), TUG (95% CI= -0.21, 0.23), ST (95% CI= -0.4, 0.91). Similarly, two groups were also no obvious distinction after THA in the 6-WMT (95% CI= -4.39, 109.82), SCP (95% CI= -1.32, 0.82), Leg extension power (95% CI= -0.14, 0.70), ST (95% CI= -5.18, 1.63). There was no difference in the incidence of adverse events. Conclusion PRT early after THA or TKA did not differ significantly from SR in terms of functional capacity, muscle strength recovery and incidence of adverse events. PRT is one of the options for rapid rehabilitation after joint replacement.

The combined effect of parathyroid hormone (1\u201334) and whole-body vibration exercise on physical performance in OSteoporotic women (PaVOS study): a secondary analysis from a randomised controlled trial

BackgroundThe aim of this study was to investigate the effect on physical performance of combining whole-body vibration exercise (WBV) with parathyroid hormone 1–34 (teriparatide) compared to teriparatide alone.MethodsA secondary analysis from a RCT where postmenopausal women with severe osteoporosis were randomised to WBV plus teriparatide (intervention) or teriparatide alone (control). WBV was applied three times/week (6x1min WBV:1 min rest, (peak acceleration 3.6 g)) for twelve months. Both groups received teriparatide 20 μg s.c./day. The primary endpoint (bone mineral density) is reported elsewhere. Physical performance measures (Short Physical Performance Battery (SPPB), Timed-Up-and-Go (TUG), leg extension power, and grip strength) were obtained at baseline, three-, six-, and twelve months, lean mass at baseline and twelve months. Data were analysed with mixed linear regression model or robust cluster regression in an intention to treat analysis.ResultsThirty-five women aged (mean ± SD) 69 ± 7) years were recruited of which thirty-two (91%) completed the twelve months follow-up (WBV + teriparatide = 15, teriparatide = 17). SPPB score (mean ± SD) improved significantly at three months in the WBV + teriparatide group from 9.13 ± 2.03 to 10.35 ± 1.69 (p = 0.014) with a statistical trend towards a between-group change in favor of the WBV + teriparatide group (0.86 [95%CI(− 0.05,1.77), p = 0.065]). Both groups improved in leg extension power during the study period whereas no changes were seen in TUG, grip strength, or lean mass in either group. No statistical significant between-group differences were observed.ConclusionWBV may improve some short-term aspects of physical performance in severely osteoporotic postmenopausal women who are receiving teriparatide treatment.Trial RegistrationClinicalTrials.gov, ID:NCT02563353