Search results for " contraction"
showing 10 items of 953 documents
Responses of serum androgenic-anabolic and catabolic hormones to prolonged strength training.
1988
Endocrine and neuromuscular effects of prolonged strength training were investigated in 21 strength-trained male subjects during the course of a 24-week progressive strength training and during a subsequent detraining period of 12 weeks. Maximal isometric leg extensor force increased by 19% (P less than 0.001) during the first 20 weeks, followed by a plateau during the 4 latest weeks of training. During the course of the training period, no systematic change was found in serum testosterone concentrations, but there was a decreasing tendency in the concentrations of free testosterone (NS), 17-OH-progesterone (NS), androstenedione (P less than 0.05), dehydroepiandrosterone (P less than 0.05),…
Acute hormonal responses to heavy resistance exercise in strength athletes versus nonathletes.
2004
The aim of the present study was to investigate acute hormonal and neuromuscular responses and recovery in strength athletes versus nonathletes during heavy resistance exercise performed with the forced and maximum repetitions training protocol. Eight male strength athletes (SA) with several years of continuous resistance training experience and 8 physically active but non-strength athletes (NA) volunteered as subjects. The experimental design comprised two loading sessions: maximum repetitions (MR) and forced repetitions (FR). MR included 12-RM squats for 4 sets with a 2-min recovery between sets. In FR the initial load was higher than in MR so that the subject could lift approximately 8 …
Adaptive response of human skeletal muscle to simulated hypergravity condition
1985
The mechanical behaviour of leg extensor muscles of five international-level athletes was evaluated during 13 months training period. Drop jumps, average mechanical power during 15 S continuous jump, and vertical jumps performed with and without extra weights were used to measure explosive power characteristics. The data recorded in vertical jumps was utilized for construction of force-velocity relationship (F-V curve). The athletes did not show improvement in any of the variables studied after 12 months of intensive systematic training programme. It was assumed that the subjects already had reached their upper limit of performance. However, after that the athletes underwent a simulated 3 w…
Vitamin C and E supplementation alters protein signalling after a strength training session, but not muscle growth during 10 weeks of training
2014
This study investigated the effects of vitamin C and E supplementation on acute responses and adaptations to strength training. Thirty-two recreationally strength-trained men and women were randomly allocated to receive a vitamin C and E supplement (1000 mg day(-1) and 235 mg day(-1), respectively), or a placebo, for 10 weeks. During this period the participants' training involved heavy-load resistance exercise four times per week. Muscle biopsies from m. vastus lateralis were collected, and 1 repetition maximum (1RM) and maximal isometric voluntary contraction force, body composition (dual-energy X-ray absorptiometry), and muscle cross-sectional area (magnetic resonance imaging) were measu…
Neuromuscular fatigue induced by an isotonic heavy-resistance loading protocol in knee extensors.
2009
Abstract The main aim of this study was to assess neuromuscular fatigue during a typical high-load, low-repetition loading protocol. Muscle stimulations were used to assess maximum voluntary contraction, resting single- and double-pulse twitch characteristics, and superimposed double-pulse twitch force (used to calculate voluntary activation) before and after an acute knee extension loading protocol. In our participants, who had previous resistance training experience, the mean voluntary activation level was 96.2% in an unfatigued state. Maximum voluntary contraction (−11.8%), resting double-pulse twitch force (−10.6%), and voluntary activation (−2.1%) were markedly decreased as a consequen…
Knee and ankle joint stiffness in sprint running.
2002
Stiffness has often been considered as a regulated property of the neuromuscular system. The purpose of this study was to examine the ankle and knee joint stiffness regulation during sprint running.Ten male sprinters ran at the constant relative speeds of 70, 80, 90, and 100% over a force platform, and ground reaction forces, kinematic, and EMG parameters were collected.The results indicated that with increasing running speed the average joint stiffness (change in joint moment divided by change in joint angle) was constant (7 N x m x deg(-1)) in the ankle joint and increased from 17 to 24 N x m x deg(-1) (P0.01) in the knee joint.The observed constant ankle joint stiffness may depend on (co…
Neuromuscular Differences Between Endurance-Trained, Power-Trained, and Sedentary Subjects
2003
This study tested the hypothesis that neuromuscular characteristics of plantar flexor (PF) and knee extensor (KE) muscles explain differences of both performance in vertical jump and maximal voluntary isometric contraction (MVC) between endurance-trained (END, n = 9), power-trained (POW, n = 8), and sedentary subjects (SED, n = 8). Evoked twitch characteristics of PF and KE were measured. MVC, maximal voluntary activation (%VA) of KE, and performance in vertical jump were also measured. POW have higher maximal rate of twitch force development (MRFD) than SED and END for both PF (p < 0.05) and KE (p < 0.01); %VA and MVC were higher for POW and END than SED (p < 0.01). Higher performances wer…
Neuromuscular fatigue following constant versus variable-intensity endurance cycling in triathletes
2008
International audience; The aim of this study was to determine whether variable power cycling produced greater neuromuscular fatigue of knee extensor muscles than constant power cycling at the same mean power output. Eight male triathletes (age : 33 ± 5 yr, mass : 74 ± 4 kg, OV&2max : 62 ± 5 ml.kg-1.min-1, maximal aerobic power : 392 ± 17 W) performed two 30 min trials on a cycle ergometer in a random order. Cycling exercise was performed either at a constant power output (CP) corresponding to 75% of the maximal aerobic power (MAP) or a variable power output (VP) with alternating ± 15%, ± 5%, and ± 10% of 75% MAP approximately every 5 min. Maximal voluntary contraction (MVC) torque, maximal…
Neural activation after maximal isometric contractions at different muscle lengths.
2006
DESBROSSES K., N. BABAULT, G. SCAGLIONI, J.-P. MEYER, and M. POUSSON. Neural Activation after Maximal Isometric Contractions at Different Muscle Lengths. Med. Sci. Sports Exerc., Vol. 38, No. 5, pp. 937–944, 2006. Purpose: To investigate i) whether neural activation dependence on muscle length is preserved with neuromuscular fatigue and ii) whether fatigue induced by a maximal isometric exercise is muscle length dependent. Methods: Twelve male subjects performed two fatiguing quadriceps muscle exercises: FS is the fatigue carried out at short muscle length (S) (S = 40- of knee flexion) and FL is the fatigue at long muscle length (L) (L = 100-). Before and after each fatiguing exercise (i.e.…
Ankle muscle strength influence on muscle activation during dynamic and static ankle training modalities.
2015
Muscle weakness is considered a risk factor for ankle injury. Balance training and barefoot running have been used in an attempt to strengthen the muscles crossing the ankle. It is expected that training tasks that successfully strengthen the ankle would elicit increased muscular activity. However, it is unknown how an individual's ankle strength will influence the muscle activity used during a given task. Twenty-six participants performed dynamic (shod, barefoot running) and static tasks (squat on ground, squat on ®Bosu Ball) believed to strengthen the muscles surrounding the ankle. Electromyographic signals of the tibialis anterior, peroneus longus, gastrocnemius lateralis (GL) and gastro…