Search results for "Isometric Contraction"
showing 10 items of 237 documents
Effects of Rapid Weight Reduction on Force Production and Vertical Jumping Height
1987
The effects of three weight reduction methods on maximal strength, rate of force development, vertical jumping height, and mechanical power were studied in track and field athletes and volleyball players. The three methods were sauna, diet with diuretic, and diuretic alone. The reductions in weight achieved were 3.4%, 5.8%, and 3.8% of body weight after sauna, diet + diuretic, and diuretic, respectively (P less than 0.001). Maximal isometric leg strength and the rate of isometric force development were decreased after the sauna and diet + diuretic treatments. Dehydration caused by the diuretic method alone did not impair neuromuscular performances. As had been expected from theoretical calc…
Isokinetic elbow flexion and coactivation following eccentric training.
1999
The influence of an eccentric training on torque/angular velocity relationships and coactivation level during maximal voluntary isokinetic elbow flexion was examined. Seventeen subjects divided into two groups (Eccentric Group EG, n = 9 Control Group CG, n = 8) performed on an isokinetic dynamometer, before and after training, maximal isokinetic elbow flexions at eight angular velocities (from - 120 degrees s(-1) under eccentric conditions to 240 degrees s(-1) under concentric conditions), and held maximal and submaximal isometric actions. Under all conditions, the myoelectric activities (EMG) of the biceps and the triceps brachii muscles were recorded and quantified as the RMS value. Eccen…
Re-examination of training effects by electrostimulation in the human elbow musculoskeletal system.
2000
This study examines the effects of a 7 weeks sub-maximal training period of electrostimulation on the maximal isometric, concentric, eccentric voluntary torque and muscle contractile properties of the elbow flexor muscles of nine subjects. The daily program consisted of five series of six 6-s isometric actions (60 to 70% of maximal isometric voluntary action) at an elbow angle of 90 . After training the maximal voluntary isometric flexion torque increased significantly whereas the maximal voluntary isometric extension torque decreased significantly. Increases in isometric flexion torque were linked to an increase of the myoelectrical activity of the biceps brachii muscle. Under dynamic cond…
Plasma catecholamine responses and neural adaptation during short-term resistance training
2000
Low exercise-induced plasma adrenaline (A) responses have been reported in resistance-trained indi- viduals. In the study reported here, we investigated the interaction between strength gain and neural adaptation of the muscles, and the plasma A response in eight healthy men during a short-term resistance-training period. The subjects performed 5 resistance exercises (E1-E5), consisting of 6 sets of 12 bilateral leg exten- sions performed at a 50% load, and with 2 days rest in between. Average electromyographic (EMG) signal amplitude was recorded before and after the exercises, from the knee extensor muscles in isometric maximal voluntary contraction (MVC) as well as during the exercises (a…
Neuromuscular efficiency of the triceps surae in induced and voluntary contractions: morning and evening evaluations.
2004
Variations in force and electromyographic (EMG) activities of skeletal muscles with the time-of-day have been previously described, but not for a postural muscle, submitted to daily postural and locomotor tasks. In this article, mechanical performances, EMGs, and the ratio between these parameters, i.e., the neuromuscular efficiency (NME), were measured on the triceps surae (TS) of eight subjects, two times each day, at 6:00 and 18:00 h. NME was evaluated under different experimental conditions (electrically induced contractions, reflex contractions, maximal and submaximal voluntary isometric contractions, and during a natural movement, a drop jump) to determine whether mechanisms, peripher…
Effects of time-of-day on neuromuscular function in untrained men: Specific responses of high morning performers and high evening performers
2015
It has been clearly established that maximal force varies during the day in human muscles but the exact mechanisms behind the diurnal rhythms are still not fully clarified. Therefore, the aim of this study was to examine the diurnal rhythms in maximal isometric force production in a large group of participants and also by separating the high morning performance types (n = 8) and the high evening performance types (n = 19) from the neutral types (n = 45) based on their actual maximal isometric force levels. Measurements were performed in the morning (7:26 h ± 63 min) and in the evening (17:57 h ± 74 min) for maximal bilateral isometric leg press force (MVCLP) together with myoelectric activi…
EMG and force production of the flexor hallucis longus muscle in isometric plantarflexion and the push-off phase of walking
2015
Large forces are generated under the big toe in the push-off phase of walking. The largest flexor muscle of the big toe is the flexor hallucis longus (FHL), which likely contributes substantially to these forces. This study examined FHL function at different levels of isometric plantarflexion torque and in the push-off phase at different speeds of walking. FHL and calf muscle activity were measured with surface EMG and plantar pressure was recorded with pressure insoles. FHL activity was compared to the activity of the calf muscles. Force and impulse values were calculated under the big toe, and were compared to the entire pressed area of the insole to determine the relative contribution of…
Plantarflexor muscle function in healthy and chronic Achilles tendon pain subjects evaluated by the use of EMG and PET imaging
2014
article i nfo Article history: Received 14 October 2013 Accepted 11 March 2014 18 F)-Fluorodeoxyglucose Background: Achilles tendon pathologies may alter the coordinative strategies of synergistic calf muscles. We hypothesized that both surface electromyography and positron emission tomography would reveal differences between symptomatic and asymptomatic legs in Achilles tendinopathy patients and between healthy controls. Methods: Eleven subjects with unilateral chronic Achilles tendon pain (28 years) and eleven matched controls (28 years) were studied for triceps surae and flexor hallucis longus muscle activity in response to repetitive iso- metric plantarflexion tasks performed at 30% of …
Short vs. Long Rest Period Between the Sets in Hypertrophic Resistance Training: Influence on Muscle Strength, Size, and Hormonal Adaptations in Trai…
2005
Acute and long-term hormonal and neuromuscular adaptations to hypertrophic strength training were studied in 13 recreationally strength-trained men. The experimental design comprised a 6-month hypertrophic strength-training period including 2 separate 3-month training periods with the crossover design, a training protocol of short rest (SR, 2 minutes) as compared with long rest (LR, 5 minutes) between the sets. Basal hormonal concentrations of serum total testosterone (T), free testosterone (FT), and cortisol (C), maximal isometric strength of the leg extensors, right leg 1 repetition maximum (1RM), dietary analysis, and muscle cross-sectional area (CSA) of the quadriceps femoris by magneti…
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 …