Noradrenaline reuptake inhibition impairs cortical output and limits endurance time

Klass, Malgorzata, Duchateau, Jacques, Rabec, Samuel, Meeusen, Romain, and Roelands, Bart (2016) Noradrenaline reuptake inhibition impairs cortical output and limits endurance time. Medicine and Science in Sports and Exercise, 48 (6). pp. 1014-1023.

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Purpose: To assess the neural mechanisms that limit endurance time, we compared a fatiguing task performed under the influence of reboxetine (REB), a noradrenaline reuptake inhibitor, and placebo (PLA).

Methods: Nine male subjects (age = 24 ± 2 yr) participated in this study. The fatiguing task involved repeated 3-s submaximal isometric contractions of the knee extensors (∼33% maximal voluntary contraction) with a 2-s rest between each contraction and performed until task failure. Before, during, and after exercise, changes in voluntary activation, corticospinal (motor-evoked potential) and spinal excitability (Hoffman reflex), and muscle contractile properties were tested using electrical and transcranial magnetic stimulations. A psychomotor vigilance task assessed reaction time before and after exercise.

Results: Compared with PLA, REB reduced the endurance time by 15.6% (P = 0.04). The maximal voluntary contraction torque decreased to a similar extent at task failure in both conditions (P < 0.01), whereas the rate of decline was greater in REB than that in PLA (P = 0.02). The level of voluntary activation tested by transcranial magnetic stimulation and electrical stimulation decreased (P < 0.01) by 10%-15% at the end of the task, but the mean rate of decline was greater in REB (P ≤ 0.03). Although motor-evoked potential did not change during fatigue, Hoffman reflex, and electrically evoked torque decreased similarly in the PLA and REB conditions (P ≤ 0.02). After exercise, reaction time increased by 3.5% (P = 0.02) in REB but did not change in the PLA condition.

Conclusion: These findings suggest that because of the noradrenaline reuptake inhibition, the output from the motor cortex is decreased at a greater rate than that in the PLA condition, contributing thereby to shorten endurance time.

Item ID: 49203
Item Type: Article (Research - C1)
ISSN: 1530-0315
Keywords: fatigue, EMG, TMS, knee extensor muscles, isometric contractions, reboxetine
Funders: Fonds National de la Recherche Scientifique (FRS-FNRS), Fund for Scientific Research Flanders (FWO), Research Council of the Université Libre de Bruxelles
Date Deposited: 07 Jun 2017 02:48
FoR Codes: 42 HEALTH SCIENCES > 4207 Sports science and exercise > 420702 Exercise physiology @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970111 Expanding Knowledge in the Medical and Health Sciences @ 100%
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