Perceived time drives physical fatigue

Abstract

Recent studies suggest that fundamental physiological processes, such as physical fatigue, rely on perceived rather than 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 (N = 24) performed 100 isometric contractions at a fixed pace and resistance in four distinct sessions. The actual contraction duration (short or long) and the calibration of the displayed clock (normal or biased toward acceleration or deceleration) were independently manipulated across sessions to examine whether fatigue and its neural correlates evolved in response to 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 involved frontal theta- and beta-band dynamics: theta modulated only under the slowed clock and beta robustly shaped by perceived time across both slowed and accelerated clocks, while motor beta showed no modulation. Further analyses highlighted the key role of frontal oscillatory dynamics in the effectiveness of the time-deception effect on physical fatigue. Significance statementCan a clock change the course of physical fatigue? In this study, we addressed this question while controlling for motivational confounds and monitoring EEG-associated power modulations. Our findings demonstrate a slowed-down fatigue accumulation in the presence of a slowed-down clock. This time manipulation effect was driven by a frontal oscillatory dynamic that largely followed the perceived time. These results highlight the direct influence of psychological factors on physiological processes and unveil the neural correlates underlying this effect.