Achraf Abdelmoula1, Stéphane Baudry2, Jacques Duchateau1. 1. Laboratory of Applied Neurophysiology and Biology, Faculty for Motor Sciences, ULB Neuroscience Institute (UNI), Université libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium. 2. Laboratory of Applied Neurophysiology and Biology, Faculty for Motor Sciences, ULB Neuroscience Institute (UNI), Université libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium. sbaudry@ulb.ac.be.
Abstract
PURPOSE: The objective of the current study was to investigate the mechanisms responsible for the briefer time to failure of a submaximal contraction (C2) when performed 60 min after a similar contraction (C1), and the influence of anodal transcranial direct current stimulation (a-tDCS) applied over the motor cortex on these mechanisms. METHODS: In two sessions, ten adults sustained two isometric contractions (35% of maximum) to failure with the abductor pollicis brevis (APB). Before C2, either a-tDCS or sham stimulation was applied over the motor cortex. Fatigue-related changes in Hoffmann (H) and long-latency (LLR) reflexes, motor-evoked potential (MEP) induced by transcranial magnetic stimulation and associated silent period (SP), maximal motor wave (Mmax), voluntary activation (VA), electromyographic (EMG) activity and peak force (PT3) evoked by a 3 pulse-train (100 Hz) were investigated. RESULTS: The results indicate that regardless of session, the time to failure was briefer (- 13%, p < 0.05) for C2 than C1, with no a-tDCS effect. During C1, MEP amplitude, SP duration and LLR amplitude increased, H-reflex amplitude did not change, and Mmax, VA and PT3 decreased (p < 0.05). Except for EMG activity that was greater during C2 than C1 (p < 0.001), all variables were similar in C1 and C2 (p > 0.05), and recovered their initial values after the 60-min rest, except PT3. CONCLUSIONS: The results of the current study indicate that a-tDCS did not influence corticospinal excitability and time to failure of C2 when performed with the APB. These observations may reflect a peripheral origin of the briefer C2 time to failure in the APB.
PURPOSE: The objective of the current study was to investigate the mechanisms responsible for the briefer time to failure of a submaximal contraction (C2) when performed 60 min after a similar contraction (C1), and the influence of anodal transcranial direct current stimulation (a-tDCS) applied over the motor cortex on these mechanisms. METHODS: In two sessions, ten adults sustained two isometric contractions (35% of maximum) to failure with the abductor pollicis brevis (APB). Before C2, either a-tDCS or sham stimulation was applied over the motor cortex. Fatigue-related changes in Hoffmann (H) and long-latency (LLR) reflexes, motor-evoked potential (MEP) induced by transcranial magnetic stimulation and associated silent period (SP), maximal motor wave (Mmax), voluntary activation (VA), electromyographic (EMG) activity and peak force (PT3) evoked by a 3 pulse-train (100 Hz) were investigated. RESULTS: The results indicate that regardless of session, the time to failure was briefer (- 13%, p < 0.05) for C2 than C1, with no a-tDCS effect. During C1, MEP amplitude, SP duration and LLR amplitude increased, H-reflex amplitude did not change, and Mmax, VA and PT3 decreased (p < 0.05). Except for EMG activity that was greater during C2 than C1 (p < 0.001), all variables were similar in C1 and C2 (p > 0.05), and recovered their initial values after the 60-min rest, except PT3. CONCLUSIONS: The results of the current study indicate that a-tDCS did not influence corticospinal excitability and time to failure of C2 when performed with the APB. These observations may reflect a peripheral origin of the briefer C2 time to failure in the APB.
Entities:
Keywords:
Electromyography; Fatigue; H reflex; Long-latency reflex; Motor-evoked potential; Transcranial magnetic stimulation
Authors: Janet L Taylor; Markus Amann; Jacques Duchateau; Romain Meeusen; Charles L Rice Journal: Med Sci Sports Exerc Date: 2016-11 Impact factor: 5.411