Optic Flow Speed During Running in a Virtual Reality Affects Perceived Time but Not Perceived Fatigue in Male Endurance Athletes

Weippert, M, Husmann, F, Schlegel, M, Bruhn, S, Feldhege, F, Mau-Moeller, A, and Behrens, M. Optic flow speed during running in a virtual reality affects perceived time but not perceived fatigue in male endurance athletes. J Strength Cond Res XX(X): 000-000, 2025-Visual feedback is directly linked to physical effort and performance in human locomotion. In this study, the effect of optic flow (OF) speed of a virtual environment during treadmill running on perceived fatigue, its potential determinants, time to exhaustion (TTE), and time perception were investigated. After familiarization, 10 endurance athletes (peak oxygen uptake: 64.6 ± 4.6 ml·min-1·kg-1) performed 2 running sessions at a speed of 90% peak oxygen uptake until exhaustion (randomized, single-blinded crossover design): treadmill-matched OF (OFMATCH, 100%) and accelerated OF (OFACC, 170%). Pre-post changes in perceived fatigue were assessed and the dynamics of potential determinants (e.g., physical strain, effort, affective valence, arousal) were quantified at regular intervals during exercise. No effects of OF were found for TTE and the psychophysiologic responses. After both running trials, duration was estimated to be shorter than chronological TTE (p ≤ 0.004, d ≥ 1.081, confidence interval [CI]: 0.272-2.351) and the ratio between perceived and chronological time was higher in the OFACC condition (OFMATCH: 0.68 ± 0.19 vs. OFACC: 0.75 ± 0.20, p = 0.015, d = -0.954, CI: -1.472 to -0.046). In conclusion, OF did not affect TTE and perceived fatigue during a short running bout until exhaustion in a virtual environment. Because elapsed time was judged significantly shorter in both conditions (i.e., "time flew"), it remains to be elucidated whether the manipulation of time perception may have an impact on running performance with a longer duration. The rate of change in affective valence predicted running performance in a linear stepwise regression analysis, suggesting that interventions with a positive effect on affective valence should be tested as potential performance enhancers.