Mind over muscle? Time manipulation improves physical performance by slowing down the neuromuscular fatigue accumulation

While physical performance has long been thought to be limited only by physiological factors, many experiments denote that psychological ones can also influence it. Specifically, the deception paradigm investigates the effect of psychological factors on performance by manipulating a psychological variable unbeknownst to the subjects. For example, during a physical exercise performed to failure, previous results revealed an improvement in performance (i.e., holding time) when the clock shown to the subjects was deceptively slowed down. However, the underlying neurophysiological changes supporting this performance improvement due to deceptive time manipulation remain unknown. Here, we addressed this issue by investigating from a neuromuscular perspective the effect of a deceptive clock manipulation on a single‐joint isometric task conducted to failure in 24 healthy participants (11 females). Neuromuscular fatigue was assessed by pre‐ to post‐exercise changes in quadriceps maximal voluntary torque (Tmax), voluntary activation level (VAL), and potentiated twitch (TTW). Our main results indicated a significant performance improvement when the clock was slowed down (Biased: 356 ± 118 s vs. Normal: 332 ± 112 s, p = .036) but, surprisingly, without any difference in the associated neuromuscular fatigue (p > .05 and BF < 0.3 for Tmax, VAL, and TTW between both sessions). Computational modeling showed that, when observed, the holding time improvement was explained by a neuromuscular fatigue accumulation based on subjective rather than actual time. These results support a psychological influence on neuromuscular processes and contribute significantly to the literature on the mind–body influence, by challenging our understanding of fatigue. Limits of physical performance can be extended by psychological manipulation. However, the fundamental mechanisms underlying this phenomenon remain unclear. Here we explore the underlying neurophysiological changes that support performance improvement due to deceptive clock manipulation. Our results showed that fatigue accumulation followed subjective rather than real time for participants who improved their performance, thus allowing to overcome physical performance limits without increasing the generated neuromuscular fatigue.