Search results for "CONTRACTIONS"
showing 10 items of 38 documents
F-contractions of Hardy–Rogers-type and application to multistage decision
2016
We prove fixed point theorems for F-contractions of Hardy–Rogers type involving self-mappings defined on metric spaces and ordered metric spaces. An example and an application to multistage decision processes are given to show the usability of the obtained theorems.
Effects of a trail running competition on muscular performance and efficiency in well-trained young and master athletes
2010
International audience; To determine the acute effects of a trail running competition and the age-dependent differences between young and master athletes, 23 subjects [10 young (30.5 ± 7 years), 13 master (45.9 ± 5.9 years)] participated in a 55-km trail running competition. The study was conceived as an intervention study compromising pre, post 1, 24, 48 and 72 h measurements. Measurements consisted of blood tests, ergometer cycling and maximal isometric voluntary contractions (MVC). Parameters monitored included MVC, twitch-and M-wave properties, EMG (RMS) of the vastus lateralis, two locomotion efficiency calculations and muscle damage markers in the blood (CK, LDH). Results indicate pos…
Alterations of mechanical characteristics of human skeletal muscle during strength training
1983
To investigate the influence of strength training on the mechanical characteristics of human skeletal muscle, 14 male subjects went through training of combined heavy concentric and eccentric contractions three times a week for 16 weeks. The strength training program consisted mainly of dynamic exercises for leg extensors with loads of 80 to 120% of one maximum repetition. The force-time curves produced during various vertical jumps were the basis for calculation of various mechanical parameters. In addition to a great increase (p less than 0.001) in maximal isometric force, heavy resistance strength training also caused significant (p less than 0.05-0.01) increases in heights and in variou…
Activation of human quadriceps femoris during isometric, concentric, and eccentric contractions.
2001
Maximal and submaximal activation level of the right knee-extensor muscle group were studied during isometric and slow isokinetic muscular contractions in eight male subjects. The activation level was quantified by means of the twitch interpolation technique. A single electrical impulse was delivered, whatever the contraction mode, on the femoral nerve at a constant 50° knee flexion (0° = full extension). Concentric, eccentric (both at 20°/s velocity), and isometric voluntary activation levels were then calculated. The mean activation levels during maximal eccentric and maximal concentric contractions were 88.3 and 89.7%, respectively, and were significantly lower ( P < 0.05) with respe…
Does a Mental Training Session Induce Neuromuscular Fatigue?
2014
ROZAND, V., F. LEBON, C. PAPAXANTHIS, and R. LEPERS. Does a Mental Training Session Induce Neuromuscular Fatigue? Med. Sci. Sports Exerc., Vol. 46, No. 10, pp. 1981–1989, 2014. Mental training, as physical training, enhances muscle strength. Whereas the repetition of maximal voluntary contractions (MVC) induces neuromuscular fatigue, the effect of maximal imagined contractions (MIC) on neuromuscular fatigue remains unknown. Here, we investigated neuromuscular alterations after a mental training session including MIC, a physical training session including MVC, and a combined training session including both MIC and MVC of the elbow flexor muscles. Methods: Ten participants performed 80 MIC (d…
Acute effects of dynamic stretching on mechanical properties result from both muscle-tendon stretching and muscle warm-up
2019
We investigated the acute effects of dynamic stretching on mechanical properties of plantar flexor muscles and tested the hypothesis that it would result from an interaction between muscle-tendon stretching and muscle warm-up. To test the stretching effect, dynamic stretching (DS) was compared to static stretching (SS). To test the warm-up effect, DS was compared to submaximal isometric muscle activity (SIMA) with similar contraction intensity. A control condition served as reference. These four conditioning activities were time matched (2×20s) and tested on separate days on 13 volunteers. Electrical neurostimulation was applied to investigate muscle mechanical properties (peak doublet torq…
Safety and feasibility of a neuromuscular electrical stimulation chronaxie-based protocol in critical ill patients: A prospective observational study
2017
International audience; Purpose: The aim of this study was to evaluate the safety and feasibility of a neuromuscular electrical stimulation (NMES) protocol based on neuromuscular excitability and applied in numerous muscle groups of critical ill patients.Materials and methods: We performed a prospective observational study using an NMES applied daily and bilaterally into 5 muscle groups in lower limbs for 3 consecutive days. The characteristics of NMES were 90 contractions per muscle, pulse width equal to chronaxie, and a pulse frequency of 100 Hz. We assessed safety with central venous oxygen saturation, serum lactate, and creatine phosphokinase measurements. To evaluate feasibility, we re…
Multi-channel electromyography during maximal isometric and dynamic contractions.
2013
Motor unit behavior differs between contraction types at submaximal contraction levels, however is challenging to study during maximal voluntary contractions (MVCs). With multi-channel surface electromyography (sEMG), mean physiological characteristics of the active motor units can be extracted. Two 8-electrode sEMG arrays were attached on biceps brachii muscle (one on each head) to examine behavior of sEMG variables during isometric, eccentric and concentric MVCs of elbow flexors in 36 volunteers. On average, isometric (364 ± 88N) and eccentric (353 ± 74N) MVCs were higher than concentric (290 ± 73N) MVC (p0.001). Mean muscle fiber conduction velocity (CV) was highest during eccentric MVC …
Neuromuscular Fatigue Following Isometric Contractions with Similar Torque Time Integral
2014
International audience; Torque time integral (TTI) is the combination of intensity and duration of a contraction. The aim of this study was to compare neuromuscular alterations following different isometric sub-maximal contractions of the knee extensor muscles but with similar TTI. Sixteen participants performed 3 sustained contractions at different intensities (25 %, 50 %, and 75 % of Maximal Voluntary Contraction (MVC) torque) with different durations (68.5 +/- 33.4 s, 35.1 +/- 16.8 s and 24.8 +/- 12.9 s, respectively) but similar TTI value. MVC torque, maximal voluntary activation level (VAL), M-wave characteristics and potentiated doublet amplitude were assessed before and immediately a…
Biceps brachii muscle oxygenation in electrical muscle stimulation
2010
The purpose of this study was to compare between electrical muscle stimulation (EMS) and maximal voluntary (VOL) isometric contractions of the elbow flexors for changes in biceps brachii muscle oxygenation (tissue oxygenation index, TOI) and haemodynamics (total haemoglobin volume, tHb = oxygenated-Hb + deoxygenated-Hb) determined by near-infrared spectroscopy (NIRS). The biceps brachii muscle of 10 healthy men (23-39 years) was electrically stimulated at high frequency (75 Hz) via surface electrodes to evoke 50 intermittent (4-s contraction, 15-s relaxation) isometric contractions at maximum tolerated current level (EMS session). The contralateral arm performed 50 intermittent (4-s contrac…