Effects of mental fatigue on exercise decision-making

Objectives: The study investigated the effects of exerting high cognitive effort on people's decisions to engage in an acute bout of exercise through a serially-mediated process involving mental fatigue and benefit vs. cost evaluations. We also examined the relationship between perceived mental fatigue, perceived exertion and behavior among participants who chose to exercise. Design. Randomized, experimenter blind to group. Method: Participants (N = 55, M-age = 19.04 +/- 1.04 years) completed either a 10-min, high cognitive demand (incongruent Stroop) task or low cognitive demand (video documentary monitoring) task. Participants then made a choice between engaging in either a 22-min self-paced moderate-to-vigorous intensity exercise task or a 22-min non-exercise task. Prior to making their choice, participants rated their mental fatigue and perceived benefits and costs of engaging in the exercise task. Results: Approximately half the sample chose to exercise (n = 30). There was no direct effect of experimental group on choice. However, serial mediation analyses revealed significant indirect effects, indicating the high cognitive demand task causes increased mental fatigue, which in turn led to lower benefit vs. cost scores, and decreased likelihood of choosing to exercise (95% C.I. = -1.03 to -0.01). Among participants who elected to exercise, mental fatigue was not associated with the amount of work performed, but positively correlated with ratings of perceived exertion while exercising. Conclusions: Findings suggest mental fatigue affects exercise decision-making by elevating subjective evaluation of the costs of engaging in exercise as opposed to sedentary alternatives.