Perceived time drives physical fatigue

Recent studies suggested that fundamental physiological processes, such as physical fatigue, rely on the perceived rather than the actual time. However, the neural correlates underlying this effect and its disentanglement from motivational factors (i.e., performance goals) remain unknown. To investigate the time deception effect on fatigue, we developed a novel EEG design in which participants performed 100 isometric contractions at a fixed pace and resistance per session. The actual contraction duration (short or long) and the calibration of the displayed clock (normal or biased to an acceleration or deceleration) were independently manipulated between sessions to examine whether fatigue and its neural correlates evolved based on perceived or actual time. Our results show an accumulation of physical fatigue that follows the perceived time, irrespective of motivational factors. This effect was consistently observed only when the clock was slowed down. This time deception effect was mediated by an oscillatory dynamic that followed perceived time in frontal (theta- and beta-bands) but not motor areas (beta-band). Further analyses highlighted the key role of the frontal oscillatory dynamics in the effectiveness of the time deception effect on physical fatigue.