Search results for " contract."
showing 10 items of 1345 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…
EMG frequency spectrum, muscle structure, and fatigue during dynamic contractions in man
1979
Fatigue of the vastus lateralis muscle was studied in healthy well-conditioned students, who differed considerable regarding their muscle fibre type distribution. Muscle force decline during repeated maximum voluntary knee extensions at a constant angular velocity (180 degree X s-1 or rad X s-1), using isokinetic equipment, was taken as the criterion for the degree of fatigue. In an attempt to study quantitative as well as qualitative changes in the EMG pattern, integrated EMG (IEMG) and the frequency of the mean power (MPF), computed from the power spectral density function (PSDF), were analysed. It was found that individuals with muscles made up of a high proportion of fast twitch (FT) mu…
Relationship between Skin Temperature, Electrical Manifestations of Muscle Fatigue, and Exercise-Induced Delayed Onset Muscle Soreness for Dynamic Co…
2020
Delayed onset muscle soreness (DOMS) indicates the presence of muscle damage and impairs force production and control. Monitorization of DOMS is useful to improving recovery intervention plans. The magnitude of DOMS may relate to muscle fatigue, which can be monitored by surface electromyography (EMG). Additionally, growing interest has been expressed in determining whether the skin temperature over a muscle group during exercise to fatigue could be a non-invasive marker for DOMS. Here we determine whether skin temperature and manifestations of muscle fatigue during exercise are correlated and can predict DOMS after concentric&ndash
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…
Continuous, bilateral Achilles' tendon vibration is not detrimental to human walk.
2001
Sensory feedback from the moving limbs contributes to the regulation of animal and human locomotion. However, the question of the specific role of the various modalities is still open. Further, functional loss of leg afferent fibres due to peripheral neuropathy does not always lead to major alteration in the gait pattern. In order to gain further insight on proprioceptive control of human gait, we applied vibratory tendon stimulation, known to recruit spindle primary afferent fibres, to both triceps surae muscles during normal floor walk. This procedure would disturb organisation and execution of walking, especially if spindles fire continuously and subjects are blindfolded. Vibration induc…
Gender variations of body composition, muscle strength and power output in morbid obesity
2005
BACKGROUND: Motor capabilities are reduced in obese (OB) individuals, and this impairment may result also from quantitative variation of muscle mass due to alterations in body composition. OBJECTIVE: This study aims to evaluate the differences in body mass (BM) and composition, as well as in muscle strength (ST) and power output W(.) between OB and NW males and females, and to test the hypothesis that variations in body composition affect muscle performance in OB subjects. DESIGN AND METHODS: Body composition (determined by BIA with a two-compartment model), upper and lower limb maximum ST (evaluated with isotonic machines) and lower limb maximum anaerobic W(.) (measured with a jumping test…
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…
The Effects of a Prolonged Running Exercise on Strength Characteristics
2000
The aim of this study was to examine concentric, isometric, and eccentric strength reductions in the quadriceps muscle following a prolonged running exercise. Before and after a 2 h run (28.4+/-1.4 km) peak torque (PT) of the knee extensors at angular velocities of -120, -90, -60, 0, 60, 120, 180, 240 degrees x s(-1) using an isokinetic dynamometer, electromyographic (EMG) activity of the vastus lateralis (VL) and vastus medialis (VM) muscles and height of a counter movement jump were recorded in twelve well-trained triathletes. Counter movement jump performances decreased by 10% and PT values were all significantly lower (p < 0.01) at each angular velocity following the run. The torque los…
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…