Individualized Mental Fatigue Does Not Impact Neuromuscular Function and Exercise Performance

Data availability statement: All data andmaterials are publicly shared on OSF at https://osf.io/xc8nr/D. S. is supported by a grant from“Ministerio de Economía, Industria y Competitividad, of Spain. D. H. is supported by a grant from “Ministerio de Universidades” of Spain and Next Generation Fonds fromthe European Union. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors have declared that no competing interests exist. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate datamanipulation. The results of the present study do not constitute endorsement by the American College of Sports Medicine.Introduction Recent studies have questioned previous empirical evidence that mental fatigue negatively impacts physical performance. The purpose of this study was to investigate the critical role of individual differences in mental fatigue susceptibility by analyzing the neurophysiological and physical responses to an individualized mental fatigue task. Methods In a preregistered (https://osf.io/xc8nr/), randomized, within-participant design experiment, 22 recreational athletes completed a time to failure test at 80% of their peak power output under mental fatigue (individual mental effort) or control (low mental effort). Before and after the cognitive tasks, subjective feeling of mental fatigue, neuromuscular function of the knee extensors, and corticospinal excitability were measured. Sequential Bayesian analysis until it reached strong evidence in favor of the alternative hypothesis (BF10 > 6) or the null hypothesis (BF10 < 1/6) were conducted. Results The individualized mental effort task resulted in a higher subjective feeling of mental fatigue in the mental fatigue condition (0.50 (95% confidence interval (CI), 0.39–0.62)) arbitrary units compared with control (0.19 (95% CI, 0.06–0.339)) arbitrary unit. However, exercise performance was similar in both conditions (control: 410 (95% CI, 357–463) s vs mental fatigue: 422 (95% CI, 367–477) s, BF10 = 0.15). Likewise, mental fatigue did not impair knee extensor maximal force-generating capacity (BF10 = 0.928) and did not change the extent of fatigability or its origin after the cycling exercise. Conclusions There is no evidence that mental fatigue adversely affects neuromuscular function or physical exercise; even if mental fatigue is individualized, computerized tasks seem not to affect physical performance.Ministerio de Economía, Industria y Competitividad of SpainMinisterio de Universidades of Spain and Next Generation Fonds from the European Unio