Prolonged mental exertion does not alter neuromuscular function of the knee extensors

Benjamin Pageaux (1, 2) , Samuele Marcora (2) , Romuald Lepers (1)

1 CAPS - Cognition, Action, et Plasticité Sensorimotrice [Dijon - U1093]
2 Endurance Research Group, School of Sport & Exercise Sciences

Purpose: The aim of this study was to test the hypotheses that prolonged mental exertion i) reduces maximal muscle activation and ii) increases the extent of central fatigue induced by subsequent endurance exercise. Methods: Neuromuscular function of the knee extensor muscles was assessed in 10 male subjects in two different conditions: i) before and after prolonged mental exertion leading to mental fatigue; ii) before and after an easy cognitive task (control). Both cognitive tasks lasted 90 min and were followed by submaximal isometric knee extensor exercise until exhaustion (endurance task), and a third assessment of neuromuscular function. Results: Time to exhaustion was 13 ± 4% shorter in the mental fatigue condition (230 ± 22s) compared to the control condition (266 ± 26 s) (P<0.01). Prolonged mental exertion did not have any significant effect on maximal voluntary contraction (MVC) torque, voluntary activation level (VAL) and peripheral parameters of neuromuscular function. A similar significant decrease in MVC torque (mental fatigue condition: -26.7 ± 5.7%; control condition: -27.6 ± 3.3%, P<0.001), VAL (mental fatigue: - 10.6 ± 4.3%; control condition: - 11.2 ± 5.2%, P<0.05) and peripheral parameters of neuromuscular function occurred in both conditions following the endurance task. However, mentally fatigued subjects rated perceived exertion significantly higher during the endurance task compared to the control condition (P < 0.05). Conclusion: These findings provide the first experimental evidence that i) prolonged mental exertion does not reduce maximal muscle activation and ii) does not increase the extent of central fatigue induced by subsequent endurance exercise. The negative effect of mental fatigue on endurance performance seems to be mediated by higher perception of effort rather than impaired neuromuscular function.

Domaines: Sciences cognitives

Benjamin Pageaux, Samuele Marcora, Romuald Lepers. Prolonged mental exertion does not alter neuromuscular function of the knee extensors. Medicine and Science in Sports and Exercise, 2013, 2013 May 21. [Epub ahead of print]. ⟨10.1249/MSS.0b013e31829b504a⟩. ⟨hal-00826836⟩