Knee Extensor Strength Research Articles

EFEITO DO TAI CHI SOBRE AS FUNÇÕES NEUROMUSCULARES NOS MEMBROS INFERIORES DOS IDOSOS

ABSTRACT Introduction: Exercise can retard the effects of aging and improve the physical function of the elderly. Tai Chi is a widespread exercise practice among the elderly in China. Although studies show the positive effects of Tai Chi practice, there is no consensus about compared studies. Objective: Evaluate the impact of regular Tai Chi exercise on neuromuscular stability in the lower limbs of elderly people, comparing the results of practitioners between sedentary and walking elderly groups. Methods: Twenty-two Tai Chi practitioners were selected, with a mean age of 59.3±3.5 years and a mean practice time of 18.4±13.2 years. This experiment mainly tests the balance ability compared to individuals practicing walking and other sedentary individuals. Results: The muscle strength of the knee flexors and extensors in the Tai Chi group was significantly greater than in the sedentary group (p=0.001 to 0.00160°/sec; P=0.002 to 60°/sec extensors; p=0.002 to 120°/sec; 120°/sec flexors, p=0.003). Similarly, there was a significant difference in muscle strength between the Tai Chi group and the walking group (the P values of the flexors and extensors at both speeds were less than 0.001). Conclusion: Tai Chi, as a regular exercise, can increase muscle strength of the general knee flexors and extensors and improve the neuromuscular stability of lower limbs in the elderly. Evidence Level II; Therapeutic Studies - Investigating the result.

Unilateral Strength Training Imparts a Cross-Education Effect in Unilateral Knee Osteoarthritis Patients.

Background: Worldwide, 86 million individuals over the age of 20 were diagnosed with knee osteoarthritis (KOA) in 2020. Hallmark features of KOA are the loss in knee extensor strength, increasing knee pain severity, and deficits in functional performance. There is a critical need for the investigation into potential cost-effective therapeutic interventions in the treatment of KOA. A potential therapeutic option is the cross-education phenomenon. Methods: This was a non-blinded randomized control trial, with a 4-week intervention, with a pre, post and follow-up assessment (3 months post intervention). Outcome measures of isometric knee extensor strength, rectus femoris muscle thickness and neuromuscular activation were assessed at all-time points. Results: Compared to age-matched KOA controls, 4 weeks of unilateral strength training in end-stage KOA patients increased strength of the untrained affected KOA limb by 20% (p < 0.05) and reduced bilateral hamstring co-activation in the KOA intervention group compared to the KOA control group (p < 0.05). Conclusions: A 4-week-long knee extensor strength training intervention of the contralateral limb in a cohort with diagnosed unilateral KOA resulted in significant improvements to knee extensor strength and improved neuromuscular function of the KOA limb. Importantly, these results were maintained for 3 months following the intervention.

Comparison of physiological responses after incremental shuttle walking test and 6-minute walk test in patients with systemic sclerosis.

The 6‑minute walk test (6MWT) is acommonly used to evaluate exercise capacity in patients with systemic sclerosis (SSc), but there was no study using the incremental shuttle walking test (ISWT) for assessing exercise capacity and comparing the patient's cardiorespiratory responses to these tests. The aim was to investigate the usability and determinants of the ISWT in patients with SSc and compare the physiological responses after the ISWT and 6MWT. A total of thirty four female patients with SSc were included. Dyspnea during daily activities and knee extensor muscle strength was assessed, skin fibrosis and disease severity were recorded, and 6MWT and ISWT were carried out for the exercise capacity measurement. Pulmonary function test results were recorded from the individuals' medical records for SSc with interstitial lung disease (SSc-ILD) patients. The ISWT distance was significantly correlated with the 6MWT distance (p < 0.001). The 6MWT was correlated with age, modified Rodnan skin score, Medsger severity score, modified British Medical Research Council Questionnaire (mMRC) score, and knee extensor muscle strength (p < 0.05). The 6MWT was correlated with the forced expiratory volume in thefirstsecond (FEV1) (lt) and forced vital capacity (FVC) (lt) in patients with SSc-ILD (p < 0.05). The ISWT distance was correlated with age, modified Rodnan skin score, mMRC score, and knee extensor muscle strength (p < 0.05). Age, mMRC, and knee extensor muscle strength explained 33.8% of the variance in 6MWT distance, while age, mMRC, and knee extensor muscle strength explained 51.7% of the variance in the ISWT distance. Because of the higher cardiopulmonary responses, and having amore standardized procedure, the ISWT may be preferable for investigating symptom-limited exercise capacity in patients with SSc. Age, dyspnea, and knee extensor muscle strength were the determinants of exercise capacity in patients with SSc.

Czynniki ograniczające zgięcie stawu kolanowego podczas chodu u dziecka z mózgowym porażeniem

Introduction: A child with cerebral palsy has multiple coexisting deficits that limit functional abilities such as walking. Their interaction shapes the kinematic gait pattern by modulating both the range and shape of the knee flexion movement during the swing phase. The significance of the effect of specific impairments on knee joint flexion range-of-motion is not clear. Aim: The aim of this study is to comprehensively analyse the effect of coexisting deficits on the range and speed of flexion at the knee joint in the sagittal plane in a child with cerebral palsy. Material and methods: In 132 patients (M = 76; F = 56; age: 11 ± 4) with spastic cerebral palsy, lower limb joint range-of-motion, selective motor control, strength and spasticity were assessed during the clinical examination. The range of knee flexion in the terminal stance phase, pre-swing and initial swing (TSt-ISw) was assessed during the laboratory three-dimensional gait analysis. Results: The TSt-ISw knee flexion movement was most strongly (RS = –0.28) dependent on knee extensor hypertonia, similarly as in the KSt stance phase (RS = –0.22) and in the KSw swing phase (RS = –0.22). The velocity of flexion (V) was most strongly correlated with knee extensor muscle hypertonia (RS = –0.32) and successively with selective control of hip flexor movement (RS = –0.28), knee extensor strength (RS = –0.23) and plantar flexor hypertonia (RS = –0.21). Conclusions: The range-of-motion of knee flexion in the sagittal plane depends on the hypertonia of the knee extensor muscles in both the TSt-ISw and KSt and KSw phases. Velocity increase depends on the occurrence of knee extensor muscle hypertonia, selective control of hip flexor movement, knee extensor strength and plantar flexor hypertonia.

A pro-inflammatory diet increases the risk of sarcopenia components and inflammatory biomarkers in postmenopausal women

Inflammation is a risk factor for muscle wasting. The dietary inflammatory index (DII) is a tool used to predict the inflammatory potential of an individual's diet. We hypothesized that consuming a potentially pro-inflammatory diet may be associated with a decreased sarcopenia component in postmenopausal women. Therefore, this study aimed to investigate the association between DII, sarcopenia components (muscle mass, muscle strength, physical performance), and inflammatory biomarkers in postmenopausal women. This cross-sectional study included 70 healthy postmenopausal women aged 50 to 80 years. The DII was calculated based on 3-day food records, and participants were divided into 3 groups according to their DII score. Skeletal muscle mass was measured using dual-energy X-ray absorptiometry. Muscle strength was assessed based on handgrip and leg muscle strength. Associations between DII and sarcopenia components and inflammatory biomarkers were determined using analysis of covariance and a general linear model after adjusting for potential confounders. The DII scores ranged from –6.08 to 5.82. Higher DII scores were significantly associated with decreased appendicular skeletal muscle (ASM) (β = –0.520), height-adjusted ASM (β = –0.116), weight-adjusted ASM (β = –0.469), knee extensor strength (β = –3.175), knee flexion strength (β = –1.941), increased body fat percentage (β = 1.238), and erythrocyte sedimentation rate (β = 5.582) (all P < .05). The present study confirmed a lower DII score, indicating that an anti-inflammatory diet is associated with higher muscle mass and strength and lower levels of inflammatory biomarkers.

Angle-specific analysis of knee strength deficits after ACL reconstruction with patellar and hamstring tendon autografts.

After anterior cruciate ligament reconstruction (ACLR), there are differences in the neuromuscular deficits observed in patients with bone-patellar tendon-bone (BPTB) and with hamstring tendon (HT) autografts. The differences in knee extensor and flexor strength are commonly reported, but analyses have largely focused on peak torque metrics despite the requirement to generate torque through range when returning to sport. The aim of this study was to investigate the angle-specific strength and strength asymmetry differences between BPTB and HT around the time of return to play after ACLR. A total of 357 male field sport athletes with either a BPTB (n=297) or an HT (n=60) autograft underwent concentric knee flexor and extensor isokinetic strength testing 9months post-ACLR. Angle-specific torques were compared between grafts and limbs using 1D Statistical Parametric Mapping and discrete-point variables. Inter-limb extensor torque asymmetry was greater in BTPB than HT at knee angles of >30° (p=0.001, peak d=5.53), with flexor torque asymmetry lower in BPTB than HT at flexion angles of >25° (p=0.001, peak d=2.68). Angle of maximum asymmetry and angle of operated limb peak torque differed in knee extension for BPTB (p < 0.001, d=0.32) but not HT, whereas knee flexion angle of maximum asymmetry and operated limb peak torque differed in both BTPB (p < 0.001, d=0.75) and HT (p < 0.001, d=0.43). Graft type affected extensor torque at knee angles of 67°-85° and flexor torque at knee angles of 27°-85°. Angle-specific strength analysis may inform the rehabilitation process and improve rehabilitation and return-to-play decision making strategies in comparison with the use of peak torque values alone.

Contribution of Different Impairments to Restricted Knee Flexion during Gait in Individuals with Cerebral Palsy.

The coexistence of overlapping impairments modulates the knee pattern in the swing phase of walking in children with cerebral palsy (CP). The impact and contribution of each impairment to the reduction of knee range-of-motion is unknown. The aim of the study was to establish the gradation of the impact of individual coexisting impairments on the knee flexion range-of-motion. Passive range-of-motion, selective motor control, strength, and spasticity from 132 patients (Male = 76, Female = 56, age:11 ± 4 years) with spastic CP were tested with clinical tools. Knee flexion range-of-motion at terminal stance, pre-swing, and initial swing phases were assessed by gait analysis. Hypertonia (β = −5.75) and weakness (β = 2.76) of knee extensors were associated with lower range of knee flexion (R2 = 0.0801, F = 11.0963, p < 0.0001). The predictive factors (R2 = 0.0744, F = 7.2135, p < 0.0001) were strength (β = 4.04) and spasticity (β = −2.74) of knee extensors and strength of hip flexors (β = −2.01); in swing those were knee extensors hypertonia (β = −2.55) and passive range of flexion (β = 0.16) (R2 = 0.0398, F = 3.4010, p = 0.01). Hypertonia of knee extensors has the strongest impact on knee flexion range-of-motion; secondary is the strength of knee extensors. The knee extensors strength with knee extensors hypertonia and strength of hip flexors contributes in stance. Knee extensors hypertonia with passive knee flexion range-of-motion contributes in swing.

Factors associated with early postoperative exercise tolerance after living-donor liver transplantation.

Physical dysfunction, including exercise intolerance, is a major factor for delayed societal reintegration for patients who underwent living-donor liver transplantation (LDLT). However, what may contribute to early postoperative physical function is not well known. The purpose of this study is to elucidate the perioperative factors affecting early posttransplant exercise intolerance. 103 consecutive patients who underwent LDLT were enrolled, and 68 patients were retrospectively analyzed. We examined the relationship between postoperative exercise tolerance evaluated by a 6-minute walking distance (6MWD) at discharge after surgery and demographic data, surgical information, preoperative physical function, clinical course, and the postoperative decline in physical function with univariate and multivariate analyses. Almost all patients were discharged within 3months after surgery. The postoperative 6MWD was 408±94 m (68 [61-84]% of the predicted value), and patients who had a low %6MWD at discharge had significantly lower preoperative physical function than patients who had a high %6MWD at discharge (grip strength: 29.8± 8.9kgf vs. 23.0±8.8 kgf, P<.01, knee extensor strength: 138.9±59.4 Nm vs. 95.2± 42.1Nm, P<.01). Multivariate analysis revealed that preoperative knee extensor strength (standardized β=0.35, P<.01) and first postoperative walking day (standardized β=-0.22, P=.04) were independently associated with the postoperative %6MWD. These results suggest that maintaining preoperative muscle strength and allowing for early postoperative mobilization might help to enhance the recovery of physical function and facilitate the patient's social reintegration after LDLT.

Use of the reliable change index to evaluate the effect of a multicomponent exercise program on physical functions.

Using the reliable change index (RCI), we aimed to examine the effect of a multicomponent exercise program on the individual level. Overall, 270 adults (mean age, 78years) completed a multicomponent physical exercise program (strength, aerobic, gait, and balance) for 40min, 1-2 times per week, continued up to 1year at a daycare center. Effectiveness was assessed using grip, ankle, knee, and hip strength; Timed Up & Go (TUG); Berg Balance Scale (BBS); gait speed; and 6-min walking distance. These were measured at baseline and every 3months thereafter. We calculated the RCI using the data between two-time points (baseline and at 3, 6, 9, or 12months) in each participant and then calculated the mean RCI value across the participants. A paired t-test was also employed to evaluate the effect of the intervention as an average-based statistics. The highest mean RCI values were on ankle plantar-flexion strength, followed by gait speed, hip abduction strength, BBS, knee extensor strength, 6-min walk distance, grip strength, and finally TUG. Paired t-test also revealed significant improvement with moderate effect sizes for ankle plantar-flexion strength (0.504), gait speed (0.413), hip abduction strength (0.374), BBS (0.334), knee extensor strength (0.264), and 6-min walk distance (0.248). Significant but small effect size was seen on TUG (0.183). The RCI is a convenient method of comparing the effect between different assessments, especially at an individual level. This index can be applied to the use of personal feedback.

Influence Of Knee Extensor Strength On Spatiotemporal Gait Parameters In Adults With Prader-willi Syndrome

Adults with Prader-Willi Syndrome (PWS) are at greater risk for falls, which may be due to impaired muscle and gait performance. PURPOSE: To compare spatiotemporal gait parameters between adults with and without PWS, and to explore associations between knee extensor strength and spatiotemporal gait parameters in adults with PWS. METHODS: 10 adults with PWS, and 10 controls with and 10 without obesity completed isometric knee extensor (KE) strength assessments and gait analyses. Strength outcomes included peak KE torque, and early and late KE rate of torque development (RTD). Gait outcomes included speed, step length, step width, double support time, cadence, and gait-stability ratio (GSR). Step length and width were normalized to height, and strength outcomes were normalized to lean mass. Gait and strength outcomes were compared between groups with one-way MANOVA, and post hoc tests were made using Tukey’s HSD. Associations between strength and gait outcomes were explored using 1-tailed Pearson and Spearman correlations in the group with PWS. RESULTS: Gait (Pillai’s Trace = 0.86, p = 0.01) and strength outcomes (Pillai’s Trace = 0.52, p = 0.01) differed between groups. Adults with PWS had shorter step length (p < 0.01), longer double support (p = 0.01), and slower gait speed (p = 0.02) compared with controls without obesity, and higher GSR compared with controls without obesity (p = 0.01) and with obesity (p = 0.04). Adults with PWS had less KE torque (p < 0.01), early (p < 0.01) and late (p < 0.001) RTD compared with controls without obesity; and less KE torque (p = 0.01), less early (p = 0.03) and late (p = 0.01) RTD. In adults with PWS, greater KE torque was associated with faster speed (rho = 0.57, p < 0.01), smaller step width (r = -0.62, p = 0.03), shorter double support time (r = -0.57, p = 0.04), and lower GSR (rho = -0.79, p < 0.01). Greater late RTD was associated a faster speed (rho = 0.79, p = 0.01), lower GSR (rho = -0.71, p = 0.01), and longer step length (rho = 0.71, p = 0.01). CONCLUSIONS: Adults with PWS have different spatiotemporal gait parameters compared with controls that contribute to slower gait speed and reduced mobility. Larger GSR may reflect an adaptive strategy to increase ground contact time and avoid dynamic portions of the gait cycle. Improving knee extensor function may be useful to increase gait performance in adults with PWS.

Analyses Of Physical Performance Determinants In Male Professional Soccer Players

Aerobic, anaerobic and anthropometric characteristics have been reported as important components of physical performance (PP) in soccer. It is theorized that better PP can enhance the degree of success and reduce risk of musculoskeletal injuries. However, evidence of how PP of each player impacts soccer team’s success is lacking, especially at the professional level. PURPOSE: To determine the effect of individual players PP on team performance success in male professional soccer league. METHODS: Cross-sectional study design with 114 male professional soccer players of the highest Czech league were classified according to team´s final league ranking into four groups: (G1) 1st-4th ranking (n = 31), (G2) 5th-8th ranking (n = 32), (G3) 9th-12th (n = 26) and (G4) 13th-16th (n = 25). PP determinants were assessed using the following indicators: Body height (BH), body weight (BW), fat mass (FM), height of vertical jump (CMJ), maximal vertical ground force (VGF), isokinetic strength (60°.s-1) of knee extensors (KE), flexors (KF) for dominant (DL) and non-dominant (NL) leg and maximal oxygen uptake (VO2max). Multivariate analyses of variances, Bonferroni post hoc test, and partial eta square (ηp2) were used for statistical assessment. RESULTS: A significant overall effect of PP on team’s performance success (p < 0.01, ηp2 = 0.16) was found. Post-hoc analyses revealed players in the G1 had significantly (p < 0.05) higher CMJ (43.70 ± 5.09 cm) compared to G3 (38.60 ± 3.98 cm) and G4 (40.40 ± 3.51 cm) players. Moreover, players in the G1 generated greater VGF (26.93 ± 2.80 N.kg-1) compare to G4 (25.14 ± 1.79 N.kg-1) and higher values of KE compare to G3 players in both DL and NL (G1: KEDL = 3.19 ± 0.47 N.m.kg-1, KENL = 3.17 ± 0.46 N.m.kg-1, G3: KEDL = 2.89 ± 0.31 N.m.kg-1, KENL = 2.87 ± 0.28 N.m.kg-1). Players in the most successful teams (G1) also showed significantly higher VO2max (60.32 ± 2.62 ml.min.kg-1) compare to players in the lowest group (G4: 57.87 ± 2.74 ml.min.kg-1). CONCLUSIONS: The current findings indicate PP including CMJ, VGF, muscle strength of KEs and VO2max of individual player is associated with final team ranks in the Czech professional soccer league. This evidence may be valuable to discuss team’s success in male professional soccer league.

Effects of total knee arthroplasty on balance and fall risk in elderly patients with severe gonarthrosis: An age- and sex-matched comparative study.

Falls are a severe cause of morbidity and mortality in elderly patients, and gonarthrosis causes a tendency to fall. Total knee arthroplasty (TKA) is a widely used successful surgical procedure for end-stage gonarthrosis. To investigate whether there is a difference in the frequency of falls, balance and fall risk, and clinical and radiological results in patients with end-stage gonarthrosis with and without TKA. This was a single-center, retrospective, case-control study with age- and gender-matched groups. A total of 100 patients over 60 years of age, with end-stage gonarthrosis and who met the inclusion criteria were included in the study. Fall risk was analyzed using the Berg Balance Scale (BBS), TUG tests, and the ITAKI Fall Risk Test. Knee varus angles were measured using standing long-leg radiographs, and radiological gonarthrosis grading was performed. Pain levels and quality of life were assessed using the VAS and WOMAC. Each patient's knee extensor muscle strength and range of motion were measured. WOMAC, ITAKI, TUG test, and VAS scores were significantly higher in the control group than in the TKA group. BBS scores were significantly lower in the control group. Although the number of falls was high in the control group, there was no statistically significant difference between the two groups. The results of this study showed that total knee arthroplasty provided statistically significant improvement in the clinical, radiological, and fall risk results of the patients. Although there was a decrease in the frequency of falls compared to the control group, it was statistically insignificant. In addition, in our study, it was evaluated that the most important risk factor for falling was advanced age.

Muscle Strength And The Onset Of Depressive Symptoms Among Older Japanese Women: The Otassha Study

Geriatric depression is a crucial public health concern. Cardiorespiratory fitness protects from the development of geriatric depression. However, the potential benefit of maintaining muscular fitness for preventing depressive symptoms remains unclear. PURPOSE: To prospectively investigate the relationship between knee extensor muscle strength and depressive symptoms in older women. METHODS: We conducted a 2-year cohort study of older Japanese women living independently in Itabashi, Tokyo, recruited through the Basic Resident Register. They underwent a baseline comprehensive geriatric examination, evaluating isometric knee extensor muscle strength (newtons/kilogram of body weight) and depressive symptoms (assessed by 15-item Geriatric Depression Scale [GDS]) via an interview-based questionnaire in 2017 or 2018. Their age, body mass index, smoking and alcohol consumption habits, comorbidities, working statuses, hobbies, volunteer activities, sleep durations, years of education, and dietary patterns were assessed as covariates. Participants free of stroke, dementia, or depression, were followed up. The onset of depressive symptoms was defined as a GDS score ≥ 5 points at follow-up. A logistic regression model was established by adjusting the baseline GDS score and the covariates. We performed a sensitivity analysis with the GDS cutoff of ≥6 points as an outcome variable. RESULTS: We recruited 1365 women in 2017 and 2018, and 1087 were eligible for this analysis. In 2019 and 2020, 642 women (mean age 71.4 years [standard deviation: 4.1]) provided valid data. Of them, 72 women (11.2%) developed depressive symptoms. After adjusting for the covariates, the odds ratio (95% confidence interval) of depressive symptoms was 0.69 (0.35, 1.33) for the middle tertile and 0.49 (0.23, 1.00) for the highest muscle strength tertiles using the lowest tertile as reference (p for trend = 0.006). The sensitivity analysis also supports a linear association between muscle strength and depression (p for trend = 0.02). CONCLUSIONS: This study suggests an inverse dose-response relationship between muscle strength and the onset of depressive symptoms in older Japanese women. It may be required to test whether muscle-strengthening training is beneficial in alleviating depressive symptoms in older women.

Bilateral Differences In Normalized Vertical And Lateral Ground Reaction Forces In Back Squats With Different Loads

The back squat is an exercise used in training for almost every sport that desires an increase in lower extremity strength. The average vertical ground reaction forces (GRFs) between the right and left legs have been compared and bilateral asymmetries have been identified (Flanagan and Salem, 2007). However, this comparison used self-defined leg dominance and did not consider the frontal plane. Additionally, the forces were not represented in terms of the combined system load (subject plus weights). PURPOSE: To determine if bilateral differences in normalized vertical and lateral GRFs exist when comparing the R and L legs, as well as legs defined by preference, dominance and strength. METHODS: Twenty subjects (10 males, 10 females) were recruited to perform a set of 5 back squat reps at 50% 1RM, 5 reps at 70% 1RM, and 3 reps at 90% 1RM with each foot on a different Kistler force plate. The middle repetition of each set was used for analysis. Knee extensor strength was determined using a Biodex System 3 isokinetic dynamometer at 60°/s. Vertical forces (Fz) were normalized by the combined subject plus load weight. RESULTS: The peak and average normalized vertical GRFs were not different based on load for any of the comparisons. The right leg created a larger normalized peak Fz (64.7% vs. 62.1%; p = 0.010) and average Fz (50.6% vs. 48.0%; p = 0.014) compared to the left leg. There was no difference in peak or average Fz based on leg preference. Dominance was determined by which foot created a larger average Fz value during the concentric phase of the squat. The dominant side created a significantly larger peak Fz (65.2% vs. 61.6%; p < 0.001) and average Fz (51.4% vs. 47.2%; p < 0.001). The stronger side created less Fz than the weaker side, but the difference was not significant. There were differences in the average lateral force based on load for all comparisons and for peak lateral force for all but leg dominance. The dominant leg created a larger average lateral force than the non-dominant leg (p = 0.009). CONCLUSION: The differences in vertical GRF based on load that have been identified previously do not exist when the forces are normalized. When comparing legs, it is important to identify the legs in terms of preference, dominance or strength. These findings can assist trainers in noting asymmetries which can increase injury risk.

Muscle Strength And Loading Patterns During Sport-related Tasks In Persons With Acetabular Dysplasia

PURPOSE: Acetabular dysplasia (AD) is described as insufficient bony coverage of the femoral head by the acetabulum that leads to joint instability, pain, and decreased function. Little is known regarding the effects of AD on muscle strength and loading patterns during sport-related tasks. We compared muscle strength and loading patterns during squat and countermovement jump (CMJ) tasks between limbs and examined associations among these variables in persons with AD. METHOD: We enrolled 12 persons with AD (11 females) and evaluated isometric strength of the knee flexors and extensors and the hip flexors, extensors, and abductors using an electromechanical dynamometer (Biodex 3). We used peak torque values (Nm/kg) for the involved and uninvolved limbs to calculate limb symmetry indices (LSI) for each muscle group. Loading patterns during a squat and CMJ takeoff and landing were evaluated using two portable force plates (ForceDecks). Average peak ground-reaction force (GRF) for the involved and uninvolved limbs (N/N) and LSI for each task were calculated. We used Wilcoxon signed-rank test to evaluate differences in muscle strength and loading patterns between limbs. We examined associations between involved limb muscle strength and loading patterns using Spearman’s rho test. RESULT: The involved limb exhibited lower knee extensor strength compared to the uninvolved limb (involved = 1.75 Nm/Kg; uninvolved = 2.11 Nm/Kg; p = 0.005). There were no other differences between limbs for the remaining muscle strength variables or for squat and CMJ loading patterns variables (all p > 0.05). Per muscle group, the following proportions exhibited ≥90% LSI: 41.7% for knee extensors and flexors and hip flexors; 66.7% for hip extensors; 90% for hip abductors. Per movement task, the following proportions exhibited ≥90% LSI: 72.7% for the squat; 90% for CMJ takeoff; 54.5% for CMJ landing. Higher hip extensor strength was associated with higher GRF during CMJ landing for involved limb (r = 0.70; p = 0.016). CONCLUSION: Persons with AD exhibited decreased involved limb knee extensor strength and asymmetric strength and loading patterns. Higher hip strength was associated with higher involved limb landing during CMJ. Further study of the associations among strength and joint loading patterns is needed in larger samples of persons with AD.

Weight Loss And Exercise Effects On Torque Development And Physical Function In Overweight Older Women

PURPOSE: Obesity negatively impacts lower extremity physical function [LEPF] and is associated with loss of independent living in part due to reduced muscle quality and capacity, especially in older women. Concurrent exercise/physical activity and weight loss interventions have been shown to improve LEPF. However, the inclusion of power modulations, specifically rate of torque development [RTD] parameters in response to these interventions has not been investigated. The aim of this study was to determine the effects of weight loss, with or without exercise training, on RTD parameters and their potential impact on LEPF in overweight physically inactive older women. METHODS: This project involved a secondary data analysis from a 6-month parent project that involved weight loss involving different dietary regimens with or without exercise. Overweight inactive postmenopausal women (n = 44, 69.1 ± 3.6 yrs; 30.6 ± 4.3 kg/m2) completed the trial within two groups: 1) exercise and weight loss [EX+WL; (N = 30)] and weight loss alone [WL; (N = 14)]. Knee flexor and extensor strength and power were assessed via a maximum voluntary contraction [MVIC] using an isokinetic dynamometry with RTD parameters [RTD200 = RTD at 200 ms, RTDPeak = Peak RTD and T2P = Time to 1st Peak]. LEPF was assessed via 6-min walk, 8-ft up and go, and 30-s chair stand. RESULTS: Weight loss was similar in the groups (-7.1 ± 4.1 kg; -9.8 ± 4.2%, p > 0.95) whereas EX+WL had greater improvements in most LEPF tasks (p < 0.001). EX+WL had a greater increase in RTD200 Flexion compared with WL (36% vs. -16%, p = 0.031), with no other differences in RTD parameters observed. No significant regression models were observed predicting change in LEPF performance from changes in RTD parameters (all p > 0.05). CONCLUSIONS: These findings suggest weight loss, which incorporates exercise training, can improve LEPF and rate of torque development in overweight/obese physically inactive older women, yet these improvements do not appear to transfer to improvements in physical function task performance

High-intensity Interval Training On Muscle Strength And Rate Of Torque Development In Female Lacrosse Players.

Sports, which include lacrosse, require sudden directional changes and rapid alterations in pace both of which are highly dependent on explosive skeletal muscle force production. Previous research has shown that high-intensity interval training (HIIT) increases maximal sprint speed, muscle power, and overall performance in field sports. Limited research on the potential of HIIT to impact skeletal muscle strength and rate of torque development in lacrosse players exist. PURPOSE: To determine the effects of HIIT in combination with lacrosse specific training on lower-limb skeletal muscle strength and rate of torque development in female high school lacrosse players (15 ± 2 yrs.). METHODS: Fourteen healthy female lacrosse players from a local high school performed HIIT three times per week in addition to their specific lacrosse training program for 11 weeks (preseason plus competitive season). Right lower-limb skeletal muscle performance was assessed Pre, Mid, and Post-HIIT training with concentric knee extensor contractions at three angular velocities (0, 1.6, and 3.1 rad·s-1). Outcome measures included: peak torque (Nm), time-to-peak torque (s), and rate of torque development (Nm·s-1). RESULTS: Isometric and concentric (3.1 rad·s-1) strength increased across the HIIT and lacrosse specific training period by 20% and 10%, respectively (p < 0.05). Combined training had no influence on time-to-peak torque (Pre: 2.2 ± 0.9 s; Post: 2.6 ± 0.5 s; p > 0.05). Rate of torque development for the first 50 ms of contraction increased by 42% at the mid-point [Pre: 607.3 ± 451.1; Mid: 862.7 ± 292.7 Nm·s-1, p < 0.05) and remained elevated at the Post-HIIT assessment (Post: 864.7 ± 255.4 Nm·s-1). No change in rate of torque development was observed over the 100-200 ms period of contraction. CONCLUSIONS: Combined HIIT with lacrosse specific training improved both static and dynamic knee extensor strength and enhanced rate of torque development within the first 50 ms of contraction in female high school lacrosse players. The inclusion of HIIT to standard pre-season and competitive lacrosse season training demonstrated no negative effects on lower-limb skeletal muscle performance.

Association of fat mass index versus appendicular lean mass index with physical function – The Yishun Study

BackgroundIncrease in body fat and reduced muscle mass are common body composition changes with age and precedes functional impairment. However, it remains unclear whether increased adiposity or less lean mass is a stronger determinant of worse functional performance. This study compared the association between fat versus lean mass indices with physical function among community-dwelling adults after adjusting for age and muscle strength. Methods542 community-dwelling adults aged between 21 and 90 years were recruited. All participants were assessed for body composition (dual X-ray absorptiometry), knee extensor strength (KES) and physical function. Fat mass and lean mass (weight in kg) were adjusted by height (in meters) squared - measured as fat mass index (FMI) and appendicular lean mass index (ALMI), respectively. Physical function was assessed using the Short Physical Performance Battery (SPPB) and the timed up and go (TUG) test. ResultsFMI was significantly associated with both SPPB (ß = -0.130, p = 0.019) and TUG (ß = 0.182, p < 0.01) after accounting for ALMI and other covariates. This association was moderated by age and KES. FMI was associated with SPPB and TUG in individuals who are older or with weaker KES. While ALMI was found to be significantly associated with TUG (ß = 0.121, p = 0.023), no significant association was found between ALMI and physical function after accounting for FMI. ConclusionsOur results show that FMI is a stronger determinant of physical function than ALMI. This emphasizes the importance of reducing body fat to mitigate functional decline especially in older and weaker adults.

Effect of Sex and Maturation on Knee Extensor and Flexor Strength in Adolescent Athletes

Background: Despite knee extensor and flexor strength reportedly being associated with injury risk, including rupture of the anterior cruciate ligament in girls, there is limited evidence for the longitudinal changes in lower extremity strength. Purpose: To investigate the sex-specific relationship with longitudinal changes of knee extensor and flexor strength associated with maturation. Study design: Cohort study; Level of evidence, 2. Methods: Adolescent boys and girls (N = 257; 208 adolsecent girls) participating in high school basketball, volleyball, and soccer were assessed longitudinally in at least 2 different pubertal stages. Pubertal status (prepubertal, pubertal, and postpubertal) was determined with the modified Pubertal Maturation Observation Scale questionnaire. After a warm-up of 5 submaximal repetitions, participants were tested for concentric peak isokinetic strength for knee extension and flexion at 300 deg/s over 10 repetitions and normalized to body weight. Linear mixed models were used to test for the effect of pubertal stage, sex, and their interaction. Results: Significant interactions were identified that indicated different maturational trajectories for knee muscle strength for adolescent boys and girls, particularly between prepubertal and pubertal stages, in which boys demonstrated greater mass normalized knee extensor increases than girls (right, +12% vs +5%; left, +13% vs +7%; P < .001). For knee flexors, boys demonstrated increased strength, while girls demonstrated decreased relative knee flexor strength (right, +4% vs −1%, P = .03; left, +3 vs −3%, P = .009). Conclusion: The findings of this study support a differential effect of sex and maturation on important knee strength outcomes that may have implications for knee injury reduction, particularly in adolescent girls as they mature.

Inter-limb asymmetries and kicking limb preference in English premier league soccer players.

The aims of this study were: (1) to quantify interlimb asymmetries in EPL soccer players in the context of kicking limb preference and (2) to establish the relationship between interlimb asymmetries and measures of physical performance. Twenty-two players (age: 21.8 ± 4.4 years) from an EPL club performed a running gait assessment (20 km/h) and unilateral countermovement jumps, a CoD assessment (modified 505 test), and an isokinetic knee extension/flexion protocol using each leg. Asymmetries were quantified using the percentage difference method and Pearson's correlations were used to quantify the association between variables. Players displayed the greatest level of asymmetry in isokinetic strength measures (5.9–12.7%) and lower levels of asymmetry in gait (1.6–7.7%), jump (0.9–7.0%) and CoD (1.9–3.5%) assessments. The influence of the preferred kicking limb was most evident in the isokinetic assessment with the players showing dominance in the preferred limb for knee flexor strength and in the non-preferred limb for knee extensor strength. These manifested in the asymmetry values calculated for the hamstring:quadricep (H:Q) ratios at 60°/s (8.80 ± 7.82%) and 240°/s (11.22 ± 7.04%) and in the functional H:Q ratio (12.67 ± 8.25%). The asymmetry values for peak extensor moment at 240°/s showed a significant correlation (ρ = −0.55, p = 0.034) with 10 m time in the CoD assessment. These findings provide benchmark asymmetry data for soccer practitioners and reveal that kicking limb preferences may bring about interlimb differences in the H:Q ratio which raises important considerations in the design of testing batteries and injury reduction interventions.