Lower Limb Muscle Function Research Articles

A 24-Week Combined Resistance and Balance Training Program Improves Physical Function in Older Adults: A Randomized Controlled Trial

Abstract Jiang, G, Tan, X, Zou, J, and Wu, X. A 24-week combined resistance and balance training program improves physical function in older adults: a randomized controlled trial. J Strength Cond Res XX(X): 000–000, 2024—This randomized controlled trial assessed the feasibility of older adults performing combined resistance and balance training (RBT) and compared the effects of RBT on physical function with those of resistance training (RT) alone and with no exercise training in older adults. In total, 65 community-dwelling adults aged 60–74 years were randomly assigned to an RT (n = 22), RBT (n = 22), or control (n = 21) group. The exercise intervention consisted of RT or RBT for 45 minutes, 3 times per week for 24 weeks. The control group engaged in no exercise training. The compliance rates were 93% in the RT group and 92% in the RBT group. No training-related adverse effect was observed. In the RT and RBT groups, dynamic balance (p = 0.017; p < 0.001, respectively), maximum walking speed (p = 0.014; p < 0.001), upper extremity (p = 0.013; p = 0.009) and lower extremity (p = 0.009; p < 0.001) muscle strength, and spirometry (p = 0.043; p = 0.018) were significantly improved at 24 weeks compared with the control group. Only the RBT group showed significant improvement in normal walking speed (p = 0.002). Compared with the RT group, the RBT group showed additional significant improvements in dynamic balance (p = 0.001) and lower limb muscle strength (p = 0.027). The findings of this randomized controlled trial indicated that RBT was safe and feasible for older adults. Long-term RBT had better effects than either no exercise training or RT alone on improving physical function in older adults. Compared with RT, RBT additionally benefited dynamic balance and lower limb muscle function, which are clinically important factors in preventing falls, frailty, disability, and other geriatric syndromes.

Five days of bed rest in young and old adults: Retainment of skeletal muscle mass with neuromuscular electrical stimulation.

The consequences of short-term disuse are well known, but effective countermeasures remain elusive. This study investigated the effects of neuromuscular electrical stimulation (NMES) during 5 days of bed rest on retaining lower limb muscle mass and muscle function in healthy young and old participants. One leg received NMES of the quadriceps muscle (3 × 30min/day) (NMES), and the other served as a control (CON). Isometric quadriceps strength (MVC), rate of force development (RFD), lower limb lean mass, and muscle thickness were assessed pre-and post-intervention. Muscle thickness remained unaltered with NMES in young and increased in old following bed rest, while it decreased in CON legs. In old participants, mid-thigh lean mass (MTLM) was preserved with NMES while decreased in CON legs. In the young, only a tendency to change with bed rest was detected for MTLM. MVC and early-phase RFD decreased in young and old, irrespective of NMES. In contrast, late-phase RFD was retained in young participants with NMES, while it decreased in young CON legs, and in the old, irrespective of NMES. NMES during short-term bed rest preserved muscle thickness but not maximal muscle strength. While young and old adults demonstrated similar adaptive responses in preventing the loss of skeletal muscle thickness, RFD was retained in the young only.

High-intensity interval training with functional electrical stimulation cycling for incomplete spinal cord injury patients: A pilot feasibility study.

Consequences of spinal cord injury (SCI) with a sedentary lifestyle will progress to muscle weakness and muscle atrophy, leading to muscle fatigue. This study aimed to determine the feasibility and preliminary effects of high-intensity interval training (HIIT) using functional electrical stimulation (FES) cycling on changes in thigh muscle volume and muscle strength, in patients with incomplete SCI. Eight incomplete SCI patients (mean age 50 years; 6 women) with stable SCI paraplegia (mean 6.75 years since injury) participated in the HIIT FES cycling (85%-90% peak Watts; 4 × 4-min intervals) three times a week (over 6 weeks). The main outcomes were adherence, participant acceptability, and adverse events. Secondary outcomes were muscle strength (peak torque) and leg volume changes. Our findings revealed that the program was well-received by participants, with high levels of adherence, positive feedback, and satisfaction, suggesting that it could be a promising option for individuals seeking to enhance their lower body strength and muscle mass. Additionally, all participants successfully completed the training without any serious adverse events, indicating that the program is safe for use. Finally, we found that the 6-week HIIT FES leg cycling exercise program resulted in notable improvements in isometric peak torque of the quadriceps (range 13.9%-25.6%), hamstring muscle (18.2%-23.3%), and leg volume (1.7%-18.2%). This study highlights HIIT FES leg cycling exercise program potential as an effective intervention for improving lower limb muscle function.

8주간의 발 각도 설정을 적용한 플라이오메트릭 훈련이 대퇴골 후경을 가진 대학 구기 종목 동아리 학생의 점프 능력 및 하지 근기능에 미치는 영향

8주간의 발 각도 설정을 적용한 플라이오메트릭 훈련이 대퇴골 후경을 가진 대학 구기 종목 동아리 학생의 점프 능력 및 하지 근기능에 미치는 영향

IZBOLJŠANJE NASTOPOV V SKUPINSKIH AKROBATSKIH SESTAVAH Z VADBO MOČI

Previous studies have highlighted a strong relationship between mechanical lower limb muscle function and TeamGym performance, specifically in terms of difficulty scores in trampette and tumbling disciplines. To date, no intervention study has explored whether enhancing lower limb muscle function can translate to improved TeamGym performance. We recruited eleven national-level TeamGym athletes (four males, seven females) for a quasi-experimental intervention spanning six weeks. The regimen comprised strength training sessions thrice weekly, emphasizing power and maximum strength. Pre- and post-intervention assessments included countermovement jumps, drop jumps, leg press power, 20m sprints, jump and reach, as well as video analyses of trampoline and tumbling performances. In line with prior research, our study uncovers significant correlations between physical test outcomes and TeamGym performance. Notably, leg press power exhibited a robust association with trampoline performance (r=0.95, p<0.001), while drop jump results correlated strongly with tumbling performance (r=0.72, p<0.05). Post-training, only the intervention group displayed a statistically likely uptick in leg press power. Additionally, the intervention group saw an average increase of 0.15±0.2 points in difficulty, contrasting with the control group's negligible change (0.0±0.2).Given the limited sample size in this preliminary pilot study, the results warrant cautious interpretation. Nonetheless, they resonate with prior findings, suggesting that augmenting an athlete's mechanical lower limb muscle function through targeted strength and power training can beneficially influence national-level TeamGym performance.

Gait balance recovery after tripping: The influence of walking speed and ground inclination on muscle and joint function

Reactive lower limb muscle function during walking plays a key role in balance recovery following tripping, and ultimately fall prevention. The objective of this study was to evaluate muscle and joint function in the recovery limb during balance recovery after trip-based perturbations during walking. Twenty-four healthy participants underwent gait analysis while walking at slow, moderate and fast speeds over level, uphill and downhill inclines. Trip perturbations were performed randomly during stance, and lower limb kinematics, kinetics, and muscle contribution to the acceleration of the whole-body centre of mass (COM) were computed pre- and post-perturbation in the recovery limb. Ground slope and walking speed had a significant effect on lower limb joint angles, net joint moments and muscle contributions to support and propulsion during trip recovery (p < 0.05). Specifically, increasing walking speed during trip recovery significantly reduced hip extension in the recovery limb and increased knee flexion, particularly when walking uphill and at higher walking speeds (p < 0.05). Gluteus maximus played a critical role in providing support and forward propulsion of the body during trip recovery across all gait speeds and ground inclinations. This study provides a mechanistic link between muscle action, joint motion and COM acceleration during trip recovery, and underscores the potential of increased walking speed and ground inclination to increase fall risk, particularly in individuals prone to falling. The findings of this study may provide guidelines for targeted exercise therapy such as muscle strengthening for fall prevention.

The Effects of Different Breathing Techniques on Lower Extremity Muscle Function and Postural Stability

OBJECTIVES This study examines the effects of bracing versus hollowing breathing techniques on lower limb muscle function and postural stability, aiming to identify the most effective breathing strategy for functional movement.METHODS Conducted on ten healthy males in their twenties without back or musculoskeletal issues, the study involved pre-experiment training in both breathing techniques. It assessed maximal strength, endurance, and power during knee flexion and extension, alongside postural stability, with both eyes open and closed, using the non-parametric Wilcoxon signed-rank test for analysis.RESULTS Except for certain specific measurements (right flexor muscle peak torque, left flexor muscle total work, and right extensor muscle power), statistical analysis showed significant differences in Knee muscle function favoring the bracing technique (p&lt;.05). While postural stability tests showed no significant overall differences between the techniques, an observable trend emerged: the hollowing group showed superior performance in one-foot balance tasks, whereas the bracing group demonstrated better outcomes in two-footed stances.CONCLUSIONS It is anticipated that bracing breathing will positively influence muscle training, surpassing the effects of hollowing by bolstering the strength, endurance, and power of the lower limbs. However, for postural stability, the hollowing technique may offer advantages in tasks requiring higher balance acuity, like one-legged standing. In contrast, bracing appears more effective for simpler stability tasks. These findings underscore breathing techniques' role in physical performance, highlighting the need for further, detailed research considering posture and musculoskeletal influences.

Effect of 12 weeks of plyometric training on explosive power, agility, and isokinetic lower limb muscle function of Taekwondo freestyle-poomsae players

Effect of 12 weeks of plyometric training on explosive power, agility, and isokinetic lower limb muscle function of Taekwondo freestyle-poomsae players

Test-retest reliability of lower limb muscle strength, jump and sprint performance tests in elite female team handball players.

This study aimed to assess the reliability of lower limb muscle function (knee extensor/flexor peak torque, rate of torque development (RTD), impulse, and countermovement jump (CMJ) performance) and sprint performance (acceleration capacity). CMJ performance was evaluated on a force plate. MVIC, RTD and impulse variables were investigated using a portable isometric dynamometer and sprint performance was assessed with dual-beam photocells in elite female athletes. CMJ test variables maximal vertical jump height, peak and mean power, concentric work, and body center of mass displacement demonstrated good-to-excellent test-retest correlations between Test 1 and Test 2 (ICC ≥ 0.70, CWw-s = 3.4-11.0%). Peak MVIC torque for the knee extensors and flexors demonstrated excellent test-retest correlations (both ICC = 0.84) along with CVw-s values of 6.8 and 6.0%, respectively. Late-phase (0-100ms, 0-200ms) RTD for the knee flexors demonstrated excellent test-retest correlations (ICC = 0.89-0.91, CVw-s = 4.8-8.5%). Sprint times at 10- and 20-m demonstrated excellent test-retest reproducibility (ICC = 0.83 and ICC = 0.90, respectively) with CVw-s values of 1.9 and 1.5%. For 5-m sprint times, test-retest reproducibility was good (ICC = 0.71) with CVw-s of 2.8%. Sprint testing performed while dribbling a handball improved (p < 0.05) from test to retest at 5-, 10- and 20-m. In conclusion, the force plate, the mobile isometric dynamometer, and dual-beam photocells provide reproducible tools for field-based testing of countermovement jump performance, knee extensor and flexor strength and sprint performance.

Effect of Botulinum Toxin Type-A on Improvement of Muscle Function of Lower Limb in Children with Spastic Cerebral Palsy

Background: Spasticity significantly contributes to the functional and postural impairments in children with cerebral palsy (CP), leading to limitations in daily independence, participation, and quality of life. Botulinum Toxin-A (BTX-A) is recognized as an effective treatment for improving outcomes related to spasticity in individuals with CP. Objectives: This study aimed to evaluate the impact of BTX-A treatment on lower limb muscle function in children with spastic CP who were unable to complete physiotherapy sessions due to muscle spasms. Methods: This cross-sectional study reviewed the medical records of 24 children with CP (14 boys, 10 girls; average age: 4.50 ± 2.70 years) who had received BTX-A injections. We recorded demographic characteristics, types of muscle dysfunction, and the number of muscles involved. BTX-A injections were administered at a dosage of 5 units/kg across multiple sites. The severity of spasticity (measured using the Ashworth scale) and motor performance (assessed by the ability to walk and stand) were evaluated 30 days after the BTX-A injection. Satisfaction levels of surgeons, physiotherapists, and parents, along with final functional outcomes, were also gathered. Data analysis was performed using SPSS. Results: The most common movement disorders observed were equinus, knee flexion, and adduction. The median score on the Ashworth scale significantly decreased (P &lt; 0.001) following BTX-A injection. There was a notable improvement in walking and standing performance (P &lt; 0.05), particularly among boys aged 3 years or younger (P &lt; 0.05). Most cases showed satisfactory outcomes 30 days after BTX-A injection. Significant enhancements in the functional outcomes of children with CP were noted after a 30-day follow-up, with no significant differences related to gender, age, or the muscles involved (P &gt; 0.05). Conclusions: The findings suggest a substantial reduction in spasticity and enhancement of functional outcomes in children with cerebral palsy after BTX-A injections. This improvement was especially evident in boys and younger children with fewer muscles involved, accompanied by notably satisfactory outcomes.

Physiological determinants of mechanical efficiency during advanced ageing and disuse.

This study aimed to determine which physiological factors impact net efficiency (ηnet) in oldest-old individuals at different stages of skeletal muscle disuse. To this aim, we examined ηnet, central haemodynamics, peripheral circulation, and peripheral factors (skeletal muscle fibre type, capillarization and concentration of mitochondrial DNA [mtDNA]). Twelve young (YG; 25 ± 2 years), 12 oldest-old mobile (OM; 87 ± 3 years), and 12 oldest-old immobile (OI; 88 ± 4 years) subjects performed dynamic knee extensor (KE) and elbow flexors (EF) exercise. Pulmonary oxygen uptake, photoplethysmography, Doppler ultrasound and muscle biopsies of the vastus lateralis and biceps brachii were used to assess central and peripheral adaptations to advanced ageing and disuse. Compared to the YG (12.1 ± 2.4%), the ηnet of lower-limb muscle was higher in the OM (17.6 ± 3.5%, P < 0.001), and lower in the OI (8.9 ± 1.9%, P < 0.001). These changes in ηnet during KE were coupled with significant peripheral adaptations, revealing strong correlations between ηnet and the proportion of type I muscle fibres (r=0.82), as well as [mtDNA] (r=0.77). No differences in ηnet were evident in the upper-limb muscles between YG, OM and OI. In view of the differences in limb-specific activity across the lifespan, these findings suggest that ηnet is reduced by skeletal muscle inactivity and not by chronological age, per se. Likewise, this study revealed that the age-related changes in ηnet are not a consequence of central or peripheral haemodynamic adaptations, but are likely a product of peripheral changes related to skeletal muscle fibre type and mitochondrial density. KEY POINTS: Although the effects of ageing and muscle disuse deeply impact the cardiovascular and skeletal muscle function, the combination of these factors on the mechanical efficiency are still a matter of debate. By measuring both upper- and lower-limb muscle function, which experience differing levels of disuse, we examined the influence of central and peripheral haemodynamics, and skeletal muscle factors linked to mechanical efficiency. Across the ages and degree of disuse, upper-limb muscles exhibited a preserved work economy. In the legs the oldest-old without mobility limitations exhibited an augmented mechanical efficiency, which was reduced in those with an impairment in ambulation. These changes in mechanical efficiency were associated with the proportion of type I muscle fibres. Recognition that the mechanical efficiency is not simply age-dependent, but the consequence of inactivity and subsequent skeletal muscle changes, highlights the importance of maintaining physical activity across the lifespan.

Perinatal HIV infection is associated with deficits in muscle function in children and adolescents in Zimbabwe.

To determine how muscle strength, power, mass, and density (i.e. quality) differ between children living with HIV (CWH) and those uninfected, and whether antiretroviral therapy (ART) regime is associated with muscle quality. A cross-sectional study in Harare, Zimbabwe. The study recruited CWH aged 8-16 years, taking ART for at least 2 years, from HIV clinics, and HIV-uninfected children from local schools. Muscle outcomes comprised grip strength measured by hand-held Jamar dynamometer, lower limb power measured by standing long-jump distance, lean mass measured by dual-energy X-ray absorptiometry, and muscle density (reflecting intramuscular fat) by peripheral quantitative computed tomography. Linear regression calculated adjusted mean differences (aMD) by HIV status. Overall, 303 CWH and 306 without HIV, had mean (SD) age 12.5 (2.5) years, BMI 17.5 (2.8), with 50% girls. Height and fat mass were lower in CWH, mean differences (SE) 7.4 (1.1) cm and 2.7 (0.4)kgs, respectively. Male CWH had lower grip strength [aMD 2.5 (1.1-3.9) kg, P < 0.001], long-jump distance [7.1 (1.8-12.5) cm, P = 0.006], muscle density [0.58 (0.12-1.05) mg/cm 3 , P = 0.018, but not lean mass 0.06 (-1.08 to 1.21) kg, P = 0.891) versus boys without HIV; differences were consistent but smaller in girls. Mediation analysis suggested the negative effect of HIV on jumping power in boys was partially mediated by muscle density ( P = 0.032). CWH taking tenofovir disoproxil fumarate (TDF) had lower muscle density [0.56 (0.00-1.13)mg/cm 3 , P = 0.049] independent of fat mass, than CWH on other ART. Perinatally acquired HIV is associated, particularly in male individuals, with reduced upper and lower limb muscle function, not mass. Intra-muscular fat (poorer muscle quality) partially explained reductions in lower limb function. TDF is a novel risk factor for impaired muscle quality.

Effect of Exercises Using Park Fitness Equipment on lower Limb Muscle Function of Inactive Women

Background and Aims This study aimed to investigate the effect of exercises using fitness equipment in parks on the lower limb muscle function of inactive women in Iran. Methods This is a prospective quasi-experimental study. The study population includes all inactive women in Tehran, Iran, aged 25-35 years. Of these, 40 women with no history of physical activity in the past year were selected using a convenience sampling method and randomly divided into two groups of control (n=20) and exercise (n=20). The training program consisted of workouts using fitness equipment in parks (sky walker, aero rider, and leg press machine) at 8 sessions, two sessions per week. The tests included Sargent jump test, triple jump test, star excursion balance test, and 6-meter single-leg timed hop test. The data were analyzed using descriptive statistics (mean and standard deviation), the Kolmogorov-Smirnov test (to examine the normal distribution of data), and the analysis of covariance (to examine differences in variables between the two groups) in SPSS software, version 24. Results After controlling the effect of pre-test scores, there was a significant difference between the two groups in the post-test score of the parameters of muscle function, indicating that exercises using the fitness equipment in parks can affect the lower limb muscle function of inactive women. Conclusion Exercises using park fitness equipment can be used to improve the lower limb muscle function of inactive women.

Core outcome set for pulmonary rehabilitation of patients with COPD: results of a modified Delphi survey

IntroductionThere is high heterogeneity of outcomes and measures reported in pulmonary rehabilitation (PR) trials of people with chronic obstructive pulmonary disease (COPD). This hinders study comparability and benchmarking of PR....

Rehabilitation Interventions for Physical Capacity and Quality of Life in Adults With Post–COVID-19 Condition

Current rehabilitation guidelines for patients with post-COVID-19 condition (PCC) are primarily based on expert opinions and observational data, and there is an urgent need for evidence-based rehabilitation interventions to support patients with PCC. To synthesize the findings of existing studies that report on physical capacity (including functional exercise capacity, muscle function, dyspnea, and respiratory function) and quality of life outcomes following rehabilitation interventions in patients with PCC. A systematic electronic search was performed from January 2020 until February 2023, in MEDLINE, Scopus, CINAHL, and the Clinical Trials Registry. Key terms that were used to identify potentially relevant studies included long-covid, post-covid, sequelae, exercise therapy, rehabilitation, physical activity, physical therapy, and randomized controlled trial. This study included randomized clinical trials that compared respiratory training and exercise-based rehabilitation interventions with either placebo, usual care, waiting list, or control in patients with PCC. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. A pairwise bayesian random-effects meta-analysis was performed using vague prior distributions. Risk of bias was assessed using the Cochrane risk of bias tool version 2, and the certainty of evidence was evaluated using the GRADE system by 2 independent researchers. The primary outcome was functional exercise capacity, measured at the closest postintervention time point by the 6-minute walking test. Secondary outcomes were fatigue, lower limb muscle function, dyspnea, respiratory function, and quality of life. All outcomes were defined a priori. Continuous outcomes were reported as standardized mean differences (SMDs) with 95% credible intervals (CrIs) and binary outcomes were summarized as odds ratios with 95% CrIs. The between-trial heterogeneity was quantified using the between-study variance, τ2, and 95% CrIs. Of 1834 identified records, 1193 were screened, and 14 trials (1244 patients; 45% female participants; median [IQR] age, 50 [47 to 56] years) were included in the analyses. Rehabilitation interventions were associated with improvements in functional exercise capacity (SMD, -0.56; 95% CrI, -0.87 to -0.22) with moderate certainty in 7 trials (389 participants). These improvements had a 99% posterior probability of superiority when compared with current standard care. The value of τ2 (0.04; 95% CrI, 0.00 to 0.60) indicated low statistical heterogeneity. However, there was significant uncertainty and imprecision regarding the probability of experiencing exercise-induced adverse events (odds ratio, 1.68; 95% CrI, 0.32 to 9.94). The findings of this systematic review and meta-analysis suggest that rehabilitation interventions are associated with improvements in functional exercise capacity, dyspnea, and quality of life, with a high probability of improvement compared with the current standard care; the certainty of evidence was moderate for functional exercise capacity and quality of life and low for other outcomes. Given the uncertainty surrounding the safety outcomes, additional trials with enhanced monitoring of adverse events are necessary.

Applicability of the seated step test for assessing thigh muscle sarcopenia in older individuals

Assessment of lower limb muscle mass and related functions in older individuals is important because of their essential role in maintaining locomotion and activities of daily living. Therefore, a simple and reliable method for assessing these parameters should be established. The seated step test is easy and safe and can be used to assess lower limb agility; however, its relationship to skeletal muscle mass and function remains unknown. The present study aimed to investigate the relationships between the seated step test and lower limb muscle mass and function. For the analysis, we included 85 participants aged 73.1 ± 6.0 years. The participants performed an alternate up-down leg step test for 10 s while seated in a chair. Lower limb muscle mass was measured using bioimpedance analysis. Skeletal muscle mass index (SMI) was calculated using the following equation: lower limb muscle mass (kg) / height2 (m2). As the muscle functional parameters, we measured the isometric knee extension peak torque (KEPT), knee flexion peak torque (KFPT), and rate of torque development (RTD) for isometric knee extension in all participants. The seated step test score had a significant relationship with KEPT, KFPT, and SMI, but not with RTD. In the single regression analysis, the seated step test significantly predicted KEPT, KFPT, and SMI. These results suggest that up-down seated step test can be a reliable method to estimate lower limb muscle size and function in older individuals.

Pistachios as a recovery food following downhill running exercise in recreational team-sport individuals

ABSTRACT We aimed to investigate the impact of pistachio nut consumption on muscle soreness and function following exercise-induced muscle damage. Using a randomised cross-over design, male team-sport players (n = 18) performed a 40-minute downhill treadmill run to induce muscle damage, which was conducted after 2-wks of consuming either control (CON, water), a standard dose of daily pistachios (STD, 42.5 g/d) or a higher dose of daily pistachios (HIGH, 85 g/d). Lower limb muscle soreness (visual analogue scale), muscle function (maximal voluntary isokinetic torque and vertical jump), and blood markers of muscle damage/inflammation (creatine kinase, C-reactive protein, myoglobin, superoxide dismutase) were measured pre (baseline) and post (24, 48, and 72 h) exercise. No trial order effects were observed for any outcome measurement across trials. Mean quadriceps soreness (non-dominant leg) during exercise recovery was reduced (p < 0.05) in HIGH vs. CON (mean difference (95%CI): 13(1–25) mm). Change in soreness in the dominant quadriceps was not different between HIGH vs. CON (p = 0.06; mean difference (95%CI): 13(−1 to 26 mm)). No main effects of time or trial were observed for mean soreness of hamstrings, or on isokinetic torque of knee extensors or knee flexors, during recovery. Serum creatine kinase concentration peaked at 24 h post-damage (mean(SEM): 763(158)µg/L) from baseline (300(87)µg/L), but had returned to baseline by 72 h post (398(80)µg/L) exercise in all trials, with no trial or trial × time interaction evident. These data suggest that high dose pistachio nut ingestion may provide some alleviation of muscle soreness, but no effect on muscle function, following modest muscle damage.

Feasibility of vertical force-velocity profiles to monitor changes in muscle function following different fatigue protocols.

This study aimed to explore the feasibility of vertical force-velocity (F-V) profiles to monitor changes in muscle function following different fatigue protocols. The between-day reliability of vertical F-V profiles and the acute effects of two fatigue protocols on the changes of lower limb muscle function were examined. Twelve resistance trained males completed a preliminary session to determine their back squat one-repetition maximum (1RM). Afterwards, they randomly performed two experimental sessions that only differed in the fatigue protocol applied: heavy-load traditional (HLT; five repetitions at 80% 1RM) and light-load ballistic (LLB; five repetitions at 30% 1RM) squat protocols. Participants' vertical F-V profiles (maximum theoretical force [F0], maximum theoretical velocity [v0], and maximum power output [Pmax]) were calculated before and immediately after each fatigue protocol. F0, v0, and Pmax showed acceptable to good between-day reliability (coefficient of variation ≤ 4.4%; intraclass correlation coefficient ≥ 0.84). Both fatigue protocols promoted a comparable reduction in Pmax (-10.1% for HLT and -12.2% for LLB). However, the LLB squat protocol reduced more v0 (-9.7%) than F0 (-0.4%), while the HLT squat protocol reduced F0 (-8.4%) more than v0 (-4.1%). The vertical F-V profile can be used to monitor changes in muscle function given its acceptable between-day reliability and its high sensitivity to detect the acute effect of force-oriented and velocity-oriented fatigue protocols on specific maximal neuromuscular capacities.

The role of the ankle plantar flexor muscles in trip recovery during walking: a computational modeling study.

Reactive lower limb muscle function during walking plays a role in balance, stability, and ultimately fall prevention. The objective of this study was to evaluate muscle and joint function used to regain balance after trip-based perturbations during walking. How are lower limb muscles used to recover from external tripping during walking? The dominant legs of 20 healthy adult participants with similar athletic backgrounds were tripped using a split-belt instrumented treadmill. High- and medium-intensity trips were simulated by deceleration of the dominant leg at initial contact from the speed of 1.1 m/s to 0 m/s and back to 1.1 m/s in 0.4 s and 0.8 s, respectively. Lower limb kinematics, kinetics, and muscle forces following perturbations were computed to pre-perturbation values using statistical parametric mapping (SPM) paired t-test. A greater ankle dorsiflexion angle (mean difference: 5.3°), ankle plantar flexion moment (mean difference: ), and gastrocnemius and soleus muscle forces (mean difference: and for GAS and SOL, respectively) were observed post-perturbation step despite the magnitude of the perturbation. This study concludes that adequate timely response of ankle function during a compensatory step is required for a successful recovery after tripping during walking in young healthy adults. Weakness in plantar flexors suggests insufficient ankle moments, which ultimately can result in falls. The findings of this paper can be used as a reference for the joint moments and range of motion needed to recover trips in the design of assistive devices. In addition to that, clinicians can use the estimated values of muscle forces and the pattern of muscle activities to design targeted training in fall prevention among the elderly.

Reference equations for quadriceps strength, endurance and power: a multicentre study.

The lack of reference values of lower-limb muscle function hinders the clinical recommendations of its measurement in patients with COPD. Therefore, this study aimed to develop reference equations to predict reference values for quadriceps strength, endurance and power and evaluate their construct validity in patients with COPD. Quadriceps strength, endurance and power were assessed in 158 healthy individuals and 87 patients with COPD. In addition, patients with COPD performed a 6-min walk test (6MWT) and a 1-min sit-to-stand test (1STS). Multiple linear regressions were performed to develop reference equations. The proportion of patients with COPD with reduced quadriceps function was determined, and correlations between quadriceps strength, endurance and power expressed in percentage of predicted values and 6MWT and 1STS performance were used to document the construct validity of the reference equation. Except for quadriceps isometric endurance, the proposed reference equations explained 50-70% of the variance of the quadriceps properties in healthy individuals. All quadriceps properties were systematically reduced in a large proportion of patients with COPD compared to healthy individuals. Correlation coefficients between quadriceps properties expressed in percentage of predicted values and 6MWT and 1STS performance ranged between 0.28 and 0.49 (all p<0.05). In healthy individuals, age, sex, height and body mass index explained 50-70% of the variance of quadriceps strength, endurance and power. When expressed in percentage of predicted values, these quadriceps properties correlated with 6MWT and 1STS performance, suggesting construct validity of the reference values in patients with COPD.