Search results for "Muscle fatigue"
showing 10 items of 161 documents
Torque decrease during submaximal evoked contractions of the quadriceps muscle is linked not only to muscle fatigue.
2015
International audience; The aim of this study was to analyze the neuromuscular mechanisms involved in the torque decrease induced by submaximal electromyostimulation (EMS) of the quadriceps muscle. It was hypothesized that torque decrease after EMS would reflect the fatigability of the activated motor units (MUs), but also a reduction in the number of MUs recruited as a result of changes in axonal excitability threshold. Two experiments were performed on 20 men to analyze 1) the supramaximal twitch superimposed and evoked at rest during EMS (Experiment 1, n = 9) and 2) the twitch response and torque-frequency relation of the MUs activated by EMS (Experiment 2, n = 11). Torque loss was asses…
Effect of exhausting stretch-shortening cycle exercise on the time course of mechanical behaviour in the drop jump: possible role of muscle damage.
1999
The purpose of the present study was to investigate the effect of stretch-shortening-cycle-induced muscle damage on the time course of mechanical behaviour in the drop jump. Ten healthy male subjects performed submaximal stretch-shortening cycle (SSC) exercise on a special sledge apparatus. Exhaustion occurred on average within 3 min. A drop jump (DJ) test from a 50-cm height was performed before and immediately after the sledge exercise as well as 2 h, 2 days and 4 days later. The fatigue exercise showed relatively high blood lactate concentration [12.5 (SD 2.6) mmol · 1−1] and an increase of serum creatine kinase (CK) activity delayed by 2 days [540 (SD 407) U · 1−1]. The initial decline …
Assessment of Fatigue and Recovery in Male and Female Athletes After 6 Days of Intensified Strength Training.
2016
Raeder, C, Wiewelhove, T, Simola, RADP, Kellmann, M, Meyer, T, Pfeiffer, M, and Ferrauti, A. Assessment of fatigue and recovery in male and female athletes after 6 days of intensified strength training. J Strength Cond Res 30(12): 3412-3427, 2016-This study aimed to analyze changes of neuromuscular, physiological, and perceptual markers for routine assessment of fatigue and recovery in high-resistance strength training. Fourteen male and 9 female athletes participated in a 6-day intensified strength training microcycle (STM) designed to purposefully overreach. Maximal dynamic strength (estimated 1 repetition maximum [1RMest]; criterion measure of fatigue and recovery); maximal voluntary iso…
Central and Peripheral Contributions to Fatigue after Electrostimulation Training
2006
Purpose: We examined the effect of 4 (WK4) and 8 wk (WK8) of neuromuscular electrical stimulation (NMES) training on both endurance time and mechanisms contributing to task failure. Methods: Ten males performed a fatiguing isometric contraction with the knee extensor muscles at 20% of maximal voluntary contraction (MVC) until exhaustion before (B), at WK4, and at WK8 of NMES training. The electromyographic (EMG) activity and muscle activation obtained under MVC were recorded before and after the fatiguing task to assess central fatigue. Torque and EMG responses obtained under electrically evoked contractions were examined before and after the fatiguing task to analyze peripheral fatigue. Re…
Neuromuscular fatigue differs with biofeedback type when performing a submaximal contraction
2007
The aim of the study was to examine alterations in contractile and neural processes in response to an isometric fatiguing contraction performed with EMG feedback (constant-EMG task) when exerting 40% of maximal voluntary contraction (MVC) torque with the knee extensor muscles. A task with a torque feedback (constant-torque task) set at a similar intensity served as a reference task. Thirteen men (26+/-5 yr) attended two experimental sessions that were randomized across days. Endurance time was greater for the constant-EMG task compared with the constant-torque task (230+/-156 s vs. 101+/-32s, P0.01). Average EMG activity for the knee extensor muscles increased from 33.5+/-4.5% to 54.7+/-21.…
Neuromuscular Fatigue After a Ski Skating Marathon
2003
The aim of this study was to characterize neuromuscular fatigue in knee extensor muscles after a marathon skiing race (mean ± SD duration = 159.7 ± 17.9 min). During the 2 days preceding the event and immediately after, maximal percutaneous electrical stimulations (single twitch, 0.5-s tetanus at 20 and 80 Hz) were applied to the femoral nerve of 11 trained skiers. Superimposed twitches were also delivered during maximal voluntary contraction (MVC) to determine maximal voluntary activation (%VA). EMG was recorded from the vastus lateralis muscle. MVC decreased with fatigue from 171.7 ± 33.7 to 157.3 ± 35.2 Nm (-8.4%; p < 0.005) while %VA did not change significantly. The RMS measured du…
Changes in corticospinal excitability during an acute bout of resistance exercise in the elbow flexors
2014
Purpose Hypertrophic resistance exercise (HRE) induces central and peripheral fatigue. However, more detailed information about changes in corticospinal excitability remains to be elucidated. Methods Eleven volunteers participated in the upper arm HRE which included one repetition maximum (1 RM) control contractions and three sets of 13 RM (SET1–3). Transcranial magnetic stimulation (TMS) was applied during maximal isometric voluntary contraction (MVC) at the end of each set and during control contractions to study changes in corticospinal excitability. Electrical stimulation was used in order to measure peripheral changes. Results MVC decreased after each set when compared to control contr…
Evolution of electromyographic signal, running economy, and perceived exertion during different prolonged exercises
2000
International audience; The purpose of this study was to compare the electromyographic (EMG) signal of the vastus lateralis muscle obtained during a run section of a triathlon and at the end of a prolonged run performed at the same running velocity. Seven subjects were studied on three occasions: a 2 h 15 min triathlon (30 min swimming, 60 min cycling, and 45 min treadmill running at 75% of the maximal aerobic speed), a 2 h 15 min run, where the last 45 min (Prolonged Run, PR) were run at the same speed as the Triathlon Run (TR) on a motorized treadmill, and a 45 min Isolated Run (IR) performed at the same TR and PR velocity. The three experimental trials were randomised. Oxygen uptake (VO …
Evidence of neuromuscular fatigue after prolonged cycling exercise
2000
International audience; Purpose: The purpose of this study was to analyze the effects of prolonged cycling exercise on metabolic, neuromuscular, and biomechanical parameters. Methods: Eight well-trained male cyclists or triathletes performed a 2-h cycling exercise at a power output corresponding to 65% of their maximal aerobic power. Maximal concentric (CON; 60, 120, 240°s 1), isometric (ISO; 0°s 1), and eccentric (ECC; 120,-60°s 1) contractions, electromyographic (EMG) activity of vastus lateralis (VL) and vastus medialis (VM) muscles were recorded before and after the exercise. Neural (M-wave) and contractile (isometric muscular twitch) parameters of quadriceps muscle were also analyzed u…
Fatigue and Recovery After High-Intensity Exercise Part II: Recovery Interventions
2004
The purpose of this study was to determine the effect of three types of recovery intervention to neuromuscular function after high-intensity uphill running exercise. The 20-min recovery interventions were (i) passive, (ii) active (running at 50 % of maximal aerobic speed), and (iii) low-frequency electromyostimulation. Evoked twitch and maximal voluntary contractions of knee extensor muscles (KE) and EMG of the vastus lateralis and vastus medialis were analysed immediately after the exercise, 10 min after the end of the recovery periods, and 65 min after the exercise (Post65). An all-out running test was also performed 80 min after the end of the fatiguing exercise. No significant differenc…