Search results for "Spinal excitability"

Effects of muscle action type on corticospinal excitability and triceps surae muscle-tendon mechanics

2014

The present study was designed to investigate corticospinal excitability modulation during maximum isometric and eccentric muscle actions with two different velocities. Moreover, the study aimed to clarify the effect of muscle action type on muscle-tendon mechanical behavior in order to shed light into the possible role of sensory information in modulating corticospinal excitability during different muscle actions. We compared motor evoked potentials (MEPs) to transcranial magnetic stimulation and Hoffman reflexes (H-reflex) in soleus muscle during isometric, slow eccentric (25 deg/s) and fast eccentric (100 deg/s) muscle actions. Concomitantly, ultrasonography was utilized to access soleus…

Longitudinal study on modulated corticospinal excitability throughout recovery in supratentorial stroke

2016

Corticospinal excitability (CSE) is modulated by stroke-induced lesions affecting the brain. This modulation is known to be dependent on the timing of the evaluation, and strongest abnormalities are often found in the acute stage. Our study aimed to characterize changes in CSE asymmetry between the affected and the unaffected hemisphere (AH and UH) during the first month after stroke onset and at 6 month follow-up. Neuronavigated transcranial magnetic stimulation (nTMS) was used to assess the CSE of the abductor pollicis brevis (APB) muscle of the hand and tibialis anterior (TA) muscle of the leg in 16 patients over 5 time-points. AH excitability recovered significantly during 6 months, whe…

Central alterations of neuromuscular function and feedback from group III-IV muscle afferents following exhaustive high-intensity one-leg dynamic exe…

2015

The aims of this investigation were to describe the central alterations of neuromuscular function induced by exhaustive high-intensity one-leg dynamic exercise (OLDE, study 1) and to indirectly quantify feedback from group III-IV muscle afferents via muscle occlusion (MO, study 2) in healthy adult male humans. We hypothesized that these central alterations and their recovery are associated with changes in afferent feedback. Both studies consisted of two time-to-exhaustion tests at 85% peak power output. In study 1, voluntary activation level (VAL), M-wave, cervicomedullary motor evoked potential (CMEP), motor evoked potential (MEP), and MEP cortical silent period (CSP) of the knee extensor…

Priming the Motor Cortex With Anodal Transcranial Direct Current Stimulation Affects the Acute Inhibitory Corticospinal Responses to Strength Trainin…

2019

Frazer, AK, Howatson, G, Ahtiainen, JP, Avela, J, Rantalainen, T, and Kidgell, DJ. Priming the motor cortex with anodal transcranial direct current stimulation affects the acute inhibitory corticospinal responses to strength training. J Strength Cond Res 33(2): 307-317, 2019-Synaptic plasticity in the motor cortex (M1) is associated with strength training (ST) and can be modified by transcranial direct current stimulation (tDCS). The M1 responses to ST increase when anodal tDCS is applied during training due to gating. An additional approach to improve the M1 responses to ST, which has not been explored, is to use anodal tDCS to prime the M1 before a bout of ST. We examined the priming effe…

Central Contribution to Electrically Induced Fatigue depends on Stimulation Frequency

2017

International audience; PURPOSE: This study analyzed the impact of several protocols of neuromuscular electrical stimulation (NMES), matched with a similar total torque-time integral, on muscle activation pathways and neuromuscular fatigue.METHODS: Ten young healthy participants (age: 24.6 +/- 4.2) performed 3 randomized NMES sessions on the triceps surae muscles with 20 Hz, 60 Hz or 100 Hz stimulation frequencies (pulse duration: 1 ms), with pulse amplitude (IES) set at 20 % of isometric maximal voluntary contraction (MVC). Muscle activity during NMES was assessed by means of the twitch, the soleus H-reflex and M wave responses evoked by single muscle stimulation at IES. Neuromuscular fati…

Acute effects of static and dynamic stretching on the neuromuscular system

2019

Stretching is traditionally incorporated into pre-exercise routines in health, rehabilitation and sporting environments to condition the neuromuscular system for exercise. While a large body of evidence reported that stretching may acutely impair the subsequent muscular performance, some conflicting results highlight possible mitigating factors of neuromuscular responses variability. Because the limited data available do not present a clear consensus, the aim of this thesis was to investigate the effects of different factors on neuromuscular responses to stretch: the muscle group, the stretch duration and modality. By means of four studies, it has been shown that static stretching may alter…

Effets aigus et chroniques de l’électrostimulation appliquée au niveau du nerf moteur : importance du retour afférent

2019

The aim of this thesis was to investigate the effects of electrical stimulation protocols favouring an indirect motor units’ (MU) recruitment via sensory axons activation and giving rise to extra force development, on the neuromuscular system. These protocols use wide pulse duration, low stimulation intensity, low and high stimulation frequencies and are applied over the motor nerve. The aim of the first study was to examine the effects of these protocols on the extent and origin of neuromuscular fatigue during an acute application. Results showed that for a similar impact on maximal force generating capacity, low stimulation frequencies limit force decreases during the stimulation trains a…

Neural contribution to postactivation potentiation

2015

The current study was designed to investigate the contribution of neural factors to postactivation potentiation (PAP). Neuromuscular function (i.e. twitches, H-reflexes, motor evoked potentials, and voluntary isometric ballistic contractions) of 8 power-trained (POW) and 8 endurance-trained (END) athletes was recorded before and after a 8-second maximal isometric conditioning contraction (CC) to induce PAP, to elucidate discriminating neural factors in exploiting PAP that might arise from the former training background compared to the latter. After CC, twitch peak force and rate of force development were significantly increased, with higher potentiation in POW (29 ± 11% and 64 ± 24%) than E…

Test-retest reliability of motor-evoked potentials at 20% and 60% of maximum isometric voluntary contraction in rectus femoris muscle

2023

Corticospinal and intracortical excitability is modulated in the knee extensors after acute strength training

2022

The corticospinal responses to high-intensity and low-intensity strength-training of the upper limb are modulated in an intensity-dependent manner. Whether an intensity-dependent threshold occurs following acute strength training of the knee extensors (KE) remains unclear. We assessed the corticospinal responses following high-intensity (85% of maximal strength) or low-intensity (30% of maximal strength) KE strength-training with measures taken during an isometric KE task at baseline, post-5, 30 and 60-min. Twenty-eight volunteers (23 ± 3 years) were randomized to high-intensity (n = 11), low-intensity (n = 10) or to a control group (n = 7). Corticospinal responses were evoked with transcra…