Dynamic Strength Of Knee Extensors Research Articles

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.

The effect of daily protein supplementation, with or without resistance training for 1 year, on muscle size, strength, and function in healthy older adults: A randomized controlled trial

Protein supplementation alone or combined with resistance training has been proposed to be effective in counteracting age-related losses of muscle mass and strength. To investigate the effect of protein supplementation alone or combined with light-intensity or heavy-load resistance exercise on muscle size, strength, and function in older adults. In a 1-y randomized controlled trial, 208 healthy older adults (>65 y) were randomly assigned to 1 of 5 interventions: 1) carbohydrate supplementation (CARB); 2) collagen protein supplementation (COLL); 3) whey protein supplementation (WHEY); 4) light-intensity resistance training 3-5 times/wk with whey protein supplementation (LITW); and 5) heavy resistance training 3 times weekly with whey protein supplementation (HRTW). Protein supplements contained 20 g protein+10 g carbohydrate, whereas CARB contained 30 g of carbohydrates. All intervention groups received the supplement twice daily. The primary outcome was change in the quadriceps cross-sectional area (qCSA). Secondary outcomes included measures of lower extremity strength and power, functional capabilities, and body composition. There were 184 participants who completed the study. COLL and WHEY did not affect any measured parameter compared to CARB. Compared to WHEY, HRTW improved the qCSA size (between-group difference, +1.68 cm2; 95% CI, +0.41 to +2.95 cm2; P=0.03), as well as dynamic (+18.4 Nm; 95% CI, +10.1 to +26.6 Nm; P<10-4) and isometric knee extensor strength (+23.9 Nm; 95% CI, +14.2 to +33.6 Nm; P<10-5). LITW did not improve the qCSA size, but increased dynamic knee extensor strength compared to WHEY (+13.7 Nm; 95% CI, +5.3 and +22.1 Nm; P=0.01). Recommending protein supplementation as a stand-alone intervention for healthy older individuals seems ineffective in improving muscle mass and strength. Only HRTW was effective in both preserving muscle mass and increasing strength. Thus, we recommend that future studies investigate strategies to increase long-term compliance to heavy resistance exercise in healthy older adults. This trial was registered at clinicaltrials.gov as NCT02034760.

Estimativa do torque muscular de extensores do joelho de idosos baseado em testes de desempenho físico funcional

Objetivo: Verificar quais métodos de avaliação clínicos de força e potência muscular, e testes de desempenho físico funcionais estão correlacionados com o pico de torque isométrico e dinâmico dos extensores de joelho, e desenvolver equações preditivas que estimem o pico de torque isométrico e dinâmico em pessoas idosas. Métodos: Foram selecionados 49 sujeitos (≥ 60 anos) de ambos os sexos. O pico de torque muscular isométrico (PTISO) e dinâmico concêntrico (PTCON) dos extensores da articulação do joelho do membro preferido foi avaliado através de dinamômetro isocinético no primeiro dia de avaliação. Quarenta e oito horas depois o teste força máxima (1-RM) unilateral do membro preferido foi executado na cadeira extensora, seguindo do teste de potência do membro superior com uma medicine ball de 2 kg (ABM-2). No terceiro dia foram avaliados o teste de equilíbrio dinâmico (time up and go), a capacidade de subir e descer escadas (separadamente), com estes três testes foi construído um índice funcional (IFUNC). Resultados: Os principais resultados demonstraram que o IFUNC não prediz melhoria no pico de torque extensor do joelho (p0,05). Contrapondo a hipótese inicial que alterações no desempenho do pico de torque, tanto isométrico, como dinâmico, teria uma resposta direta com o desempenho funcional. Conclusão: As medidas de força máxima para membro inferior (cadeira extensora-1-RM) e potência de membro superior (arremesso da bola de medicine ball 2-kg) quando associadas explicam com mais de 60% (p0,05) uma mudança no desempenho na força isométrica e dinâmica dos extensores de joelho de idosos não treinados.

Strength training and aerobic exercise training for muscle disease.

Background Strength training or aerobic exercise programmes might optimise muscle and cardiorespiratory function and prevent additional disuse atrophy and deconditioning in people with a muscle disease. This is an update of a review first published in 2004. Objectives To examine the safety and efficacy of strength training and aerobic exercise training in people with a muscle disease. Search methods We searched the Cochrane Neuromuscular Disease Group Specialized Register (July 2012), CENTRAL (2012 Issue 3 of 4), MEDLINE (January 1946 to July 2012), EMBASE (January 1974 to July 2012), EMBASE Classic (1947 to 1973) and CINAHL (January 1982 to July 2012). Selection criteria Randomised or quasi-randomised controlled trials comparing strength training or aerobic exercise programmes, or both, to no training, and lasting at least six weeks, in people with a well-described diagnosis of a muscle disease. We did not use the reporting of specific outcomes as a study selection criterion. Data collection and analysis Two authors independently assessed trial quality and extracted the data obtained from the full text-articles and from the original investigators. We collected adverse event data from included studies. Main results We included five trials (170 participants). The first trial compared the effect of strength training versus no training in 36 people with myotonic dystrophy. The second trial compared aerobic exercise training versus no training in 14 people with polymyositis and dermatomyositis. The third trial compared strength training versus no training in a factorial trial that also compared albuterol with placebo, in 65 people with facioscapulohumeral muscular dystrophy (FSHD). The fourth trial compared combined strength training and aerobic exercise versus no training in 18 people with mitochondrial myopathy. The fifth trial compared combined strength training and aerobic exercise versus no training in 35 people with myotonic dystrophy type 1. In both myotonic dystrophy trials and the dermatomyositis and polymyositis trial there were no significant differences between training and non-training groups for primary and secondary outcome measures. The risk of bias of the strength training trial in myotonic dystrophy and the aerobic exercise trial in polymyositis and dermatomyositis was judged as uncertain, and for the combined strength training and aerobic exercise trial, the risk of bias was judged as adequate. In the FSHD trial, for which the risk of bias was judged as adequate, a +1.17 kg difference (95% confidence interval (CI) 0.18 to 2.16) in dynamic strength of elbow flexors in favour of the training group reached statistical significance. In the mitochondrial myopathy trial, there were no significant differences in dynamic strength measures between training and non-training groups. Exercise duration and distance cycled in a submaximal endurance test increased significantly in the training group compared to the control group. The differences in mean time and mean distance cycled till exhaustion between groups were 23.70 min (95% CI 2.63 to 44.77) and 9.70 km (95% CI 1.51 to 17.89), respectively. The risk of bias was judged as uncertain. In all trials, no adverse events were reported. Authors' conclusions Moderate-intensity strength training in myotonic dystrophy and FSHD and aerobic exercise training in dermatomyositis and polymyositis and myotonic dystrophy type I appear to do no harm, but there is insufficient evidence to conclude that they offer benefit. In mitochondrial myopathy, aerobic exercise combined with strength training appears to be safe and may be effective in increasing submaximal endurance capacity. Limitations in the design of studies in other muscle diseases prevent more general conclusions in these disorders.

Influence of between-limb asymmetry in muscle mass, strength, and power on functional capacity in healthy older adults.

Numerous daily tasks such as walking and rising from a chair involve bilateral lower limb movements. During such tasks, lower extremity function (LEF) may be compromised among older adults. LEF may be further impaired due to high degrees of between-limb asymmetry. The present study investigated the prevalence of between-limb asymmetry in muscle mass, strength, and power in a cohort of healthy older adults and examined the influence of between-limb asymmetry on LEF. Two hundred and eight healthy older adults (mean age 70.2±3.9years) were tested for LEF (400m walking and 30-seconds chair stand). Furthermore, maximal isometric and dynamic knee extensor strength, leg extensor power, and lower limb lean tissue mass (LTM) were obtained unilaterally. Mean between-limb asymmetry in maximal muscle strength and power ranged between 10% and 13%, whereas LTM asymmetry was 3±2.3%. Asymmetry in dynamic knee extensor strength was larger for women compared with men (15.0±11.8% vs 11.1±9.5%; P=.005) Leg strength and power were positively correlated with LEF (r2 =.43-.46, P<.001). The weakest leg was not a stronger predictor of LEF than the strongest leg. Between-limb asymmetry in LTM and isometric strength was negatively associated with LEF (LTM; r2 =.12, P=.005, isometric peak torque; r2 =0.40, P=.03.) but dynamic strength and power were not. The present study supports the notion that in order to improve or maintain LEF, healthy older adults should participate in training interventions that increase muscle strength and power, whereas the effects of reducing between-limb asymmetry in these parameters might be of less importance.

Water-based aerobic training improves strength parameters and cardiorespiratory outcomes in elderly women.

The aim of the present study was to compare the effects of water-based aerobic training and water-based resistance training on muscular strength and cardiorespiratory fitness in older women. Sixty-nine individuals were randomized into the following three groups: the water-based aerobic training (WA, n = 23) group, the water-based resistance training (WR, n = 23) group, and the control group (CG, n = 23). Participants were trained two times per week for 10 weeks. The trainings presented a linear periodization with an increase in the volume-intensity relation. Maximal dynamic muscular strength and the cardiorespiratory fitness were evaluated before the start of training and after 10 weeks of training. Only the WA group showed an increase in maximal oxygen consumption (13.8%) and oxygen consumption at the second ventilatory threshold (16.4%). Maximal dynamic strength of knee extensors improved in 10.6% of WA, 8.0% of WR, and 4.7% of CG participants, without any difference between the groups. Maximal dynamic strength of knee flexors was increased in 14.1% of WA and in 17.7% of WR participants; however, it remains unchanged in CG participants. No differences were observed in resting heart rate, peak heart rate, heart rate at the second ventilatory threshold and maximal dynamic strength of shoulder horizontal flexors. It was concluded that WA seems to be more efficient for improvement in cardiorespiratory responses, and both WA and WR were efficient for development of maximal dynamic strength of knee flexion and extension.

Changes in static and dynamic knee extensor strength after TKA

Changes in static and dynamic knee extensor strength after TKA

MSTN mRNA After Varying Exercise Modalities in Humans

The aim of this study was to examine the effects of strength and endurance training on myostatin mRNA in the vastus lateralis muscle of healthy and physically active humans. 21 healthy and physically active sports students (static and dynamic knee extensor strength 33 ± 4.5 N/kgBW; 1 185 ± 170 W, respectively; maximum oxygen uptake 52.5 ± 8 ml/kgBW/min) were recruited and randomly assigned to a moderate endurance training group (n=7), a strength training group (n=7) and a control group (n=7). Muscle biopsies were taken from the vastus lateralis muscle 3-5 days before the start as well as at the end of the 12 weeks' training period. Exercise-specific functional improvements after moderate endurance training and strength training were measured for submaximal endurance and for static and dynamic strength of the knee extensor muscles. None of the myostatin mRNA values showed significant pre-post differences or group-specific differences. These results are in contrast to data with sedentary subjects, suggesting that myostatin is necessary for adaptations of skeletal muscle to exercise stress. We conclude that functional improvements after moderate endurance training and strength training can occur without alterations in myostatin mRNA in physically active humans.

The effect of exercise-induced muscle damage on isometric and dynamic knee extensor strength and vertical jump performance

In this study, we assessed the effect of exercise-induced muscle damage on knee extensor muscle strength during isometric, concentric and eccentric actions at 1.57 rad · s -1 and vertical jump performance under conditions of squat jump, countermovement jump and drop jump. The eight participants (5 males, 3 females) were aged 29.5 - 7.1 years (mean - s ). These variables, together with plasma creatine kinase (CK), were measured before, 1 h after and 1, 2, 3, 4 and 7 days after a bout of muscle damaging exercise: 100 barbell squats (10 sets 2 10 repetitions at 70% body mass load). Strength was reduced for 4 days ( P ≪ 0.05) but no significant differences ( P > 0.05) were apparent in the magnitude or rate of recovery of strength between isometric, concentric and eccentric muscle actions. The overall decline in vertical jump performance was dependent on jump method: squat jump performance was affected to a greater extent than countermovement (91.6 - 1.1% vs 95.2 - 1.3% of pre-exercise values, P ≪ 0.05) and drop jump (95.2 - 1.4%, P ≪ 0.05) performance. Creatine kinase was elevated ( P ≪ 0.05) above baseline 1 h after exercise, peaked on day 1 and remained significantly elevated on days 2 and 3. Strength loss after exercise-induced muscle damage was independent of the muscle action being performed. However, the impairment of muscle function was attenuated when the stretch-shortening cycle was used in vertical jumping performance.