INTRODUCTION

A growing body of literature showed that mental fatigue induced by an effortful task leads to an impairment in a subsequent physical performance. The principal aim of this experimental study was to reproduce the effect of mental fatigue on endurance performance while investigating the effort deployment in the fatiguing and control tasks that precede the physical task.

METHODS

Participants performed the following task sequence in a between-subjects design ( = 16 in each group): a time-to-exhaustion handgrip task at 13% of maximal voluntary contraction, a 30-min mental task (Stroop task or documentary watching task) and the handgrip task again. Psychophysiological data were recorded on a continuous basis during the whole experiment.

RESULTS

Mental fatigue was induced successfully: behavioral and psychophysiological data suggest gradual disengagement of effort in the fatiguing task but not in the control task (increased reaction time and error rate as the function of time in the Stroop task; higher mid-frontal theta during the Stroop task compared to the control task; decreased stimulus-locked theta rhythm over time during the Stroop task; increased low frequency heart rate variability during the Stroop task). In addition, performance decrement in the time to exhaustion handgrip task was larger after the Stroop task than after the documentary viewing task ( 0.818).

CONCLUSION

This study highlights the importance of assessing both performance and effort engagement to understand mental fatigue. Despite signs of effort disengagement during the Stroop task, mental fatigue still impaired the subsequent physical performance.