Abstract
Mental exertion is known to impair endurance performance, but its effects on neuromuscular function remain unclear. The purpose of this study was to test the hypothesis that mental exertion reduces torque and muscle activation during intermittent maximal voluntary contractions of the knee extensors. Ten subjects performed in a randomized order three separate mental exertion conditions lasting 27 min each: (i) high mental exertion (incongruent Stroop task), (ii) moderate mental exertion (congruent Stroop task), (iii) low mental exertion (watching a movie). In each condition, mental exertion was combined with 10 intermittent maximal voluntary contractions of the knee extensor muscles (one maximal voluntary contraction every 3 min). Neuromuscular function was assessed using electrical nerve stimulation. Maximal voluntary torque, maximal muscle activation and other neuromuscular parameters were similar across mental exertion conditions and did not change over time. These findings suggest that mental exertion does not affect neuromuscular function during intermittent maximal voluntary contractions of the knee extensors.
Highlights
Mental exertion refers to the engagement with a demanding cognitive task
Follow-up tests revealed that subjects rated fatigue lower in the control condition compared to the moderate mental exertion condition (p < 0.05)
Neither high mental exertion nor moderate mental exertion altered maximal force production and maximal muscle activation during intermittent maximal voluntary contraction (MVC) of the knee extensors. These findings demonstrate that the combination of intermittent MVCs and high mental exertion does not reduce the capacity of the central nervous system (CNS) to drive to the working muscles
Summary
Mental exertion refers to the engagement with a demanding cognitive task. When performed simultaneously to physical exertion, mental exertion is known to impair endurance performance (Yoon et al, 2009; Mehta and Agnew, 2012). Even with 90 min of prior mental exertion induced by the AX-CP test, Pageaux et al (2013) demonstrated that prolonged mental exertion does not induce a decrease in MVC torque of the knee extensor muscles. Together, these results suggest that mental exertion does not alter maximal force production. The authors found a significant reduction in maximal force production during the last MVC of this experimental protocol These results suggest a possible interaction between intermittent MVCs and high mental exertion on maximal force production
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