Search results for "Voluntary activation"
showing 10 items of 12 documents
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…
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…
Neuromuscular adaptations to combined strength and endurance training: order and time-of-day
2017
AbstractThe present study examined the effects of 24 weeks of morning vs. evening same-session combined strength (S) and endurance (E) training on neuromuscular and endurance performance. Fifty-one men were assigned to the morning (m) or evening (e) training group, where S preceded E or vice versa (SEm, ESm, SEe and ESe), or to the control group. Isometric force, voluntary activation, EMG and peak wattage during the maximal cycling test were measured. Training time did not significantly affect the adaptations. Therefore, data are presented for SEm+e (SEm+SEe) and ESm+e (ESm+ESe). In the morning, no order specific gains were observed in neuromuscular performance. In the evening, the changes …
Neuromuscular fatigue following high versus low-intensity eccentric exercise of biceps brachii muscle
2009
International audience; Purpose: This study investigated neuromuscular fatigue following high versus low-intensity eccentric exercise corresponding to the same amount of work.Methods: Ten volunteers performed two eccentric exercises of the elbow flexors: a high-intensity versus a low-intensity exercise. Maximal voluntary contraction torque and surface electromyography of the biceps brachii muscle were recorded before, immediately and 48 h after exercises. Maximal voluntary activation level, neural (M-wave) and contractile (muscular twitch) properties of the biceps brachii muscle were analysed using electrical stimulation techniques.Results: Maximal voluntary contraction torque was significa…
Neural Activation During Submaximal Contractions Seems More Reflective of Neuromuscular Ageing than Maximal Voluntary Activation
2016
International audience; This study aimed at testing the hypothesis that differences in neural activation strategy during submaximal but not maximal plantarflexions exist between young and older men. Eleven young men (YM, 26 +/- 4 years) and thirteen old men (OM, 76 +/- 3 years) volunteered for the investigation. Maximal voluntary torque (MVT) was 38.2%, lower (p < 0.001) in OM than in YM, while voluntary activation was equivalent (similar to 97%). The relationship between the interpolated twitch torque and the voluntary torque (IT-VT relationship) was composite (curvilinear + exponential) for both age-groups. However, the OM showed accentuated concavity, as attested by the occurrence of the…
Transcranial direct current stimulation improves isometric time to exhaustion of the knee extensors
2016
International audience; Transcranial direct current stimulation (tDCS) can increase cortical excitability of a targeted brain area, which may affect endurance exercise performance. However, optimal electrode placement for tDCS remains unclear. We tested the effect of two different tDCS electrode montages for improving exercise performance. Nine subjects underwent a control (CON), placebo (SHAM) and two different tDCS montage sessions in a randomized design. In one tDCS session, the anodal electrode was placed over the left motor cortex and the cathodal on contralateral forehead (HEAD), while for the other montage the anodal electrode was placed over the left motor cortex and cathodal electr…
Dépendance de la fatigue à la longueur musculaire : approche mécanique et neurophysiologique
2006
The objective of this work is to evaluate the fatigue dependency on the knee extensor muscles length. Exercises varying the type of contraction (isometric and eccentric) and intensity of contraction (maximal and sub-maximal) are performed in order to disrupt the neuromuscular system by different factors of fatigue: central and peripheral. These exercises are performed at two muscular lengths (S and L, corresponding respectively to 40 and 100° of knee flexion). Neuromuscular parameters (maximal torque, muscular twitch, voluntary activation level, electromyographic activity, etc.) are analyzed in pre- and post-fatigue conditions in the type of contraction required by the fatiguing exercise. I…
Adaptations neuromusculaires des muscles extenseurs du genou : contractions fatigantes uni- vs bi-latérales
2010
The aim of this work was to determine i) the influence of the level of absolute force on the duration of the endurance time, and subsequent neuromuscular alterations in same individual at the end of an exercise performed at the same relative intensity, with one or two legs, ii) the influence of central drive on the force capacity production of the knee extensor muscles during unilateral (UL) vs. bilateral (BL) contractions, iii) activation mechanisms evolution for a serie of submaximal evoked contractions by electrostimulation (EMS). The results of the first study confirm that the endurance limit depends on the level of absolute force for the same individual, contraction duration for UL is …
Optimal inter-stimulus interval for interpolated twitch technique when using double pulse stimulation
2013
Interpolated twitch technique is a method frequently used to assess voluntary activa- tion. This method uses electrically evoked twitch superimposed on the voluntary activi- ty and its comparison with the twitch in rested muscle i.e. control twitch, to evaluate completeness of muscle activation. The purpose of this study was to investigate the ef- fect of interval in paired stimulation on control twitch in young and elderly individuals with bent and flexed knee positions. Supramaximal electrical stimulation consisted of one single stimulus and eight paired stimulation with intervals from 5 to 40ms, with increments of 5ms. In evoked twitches normalized peak torque amplitude (NPT), time to pe…
Neural Adaptations to Strength Training
2018
Scientific study of strength training has revealed numerous physiological mechanisms that contribute to: (1) acute fatigue from a single strength training session and (2) chronic adaptation to repetitive and systematic strength training. Therefore, the purpose of this chapter is initially to discuss potential neural mechanisms that influence force production from the perspective of a single repetition. Thereafter, the chapter will highlight scientific evidence for candidate neural mechanisms that acutely limit force production during a single strength training session and long-term adaptations caused by strength training. For some of these potential neural mechanisms, there is strong scient…