Cognitive Fatigue Disrupts Explosive Performance and Vigilance in Trained Individuals

This study examined the effects of cognitive fatigue on repeated sprint ability (RSA), neuromuscular performance, and vigilance in physically active young adults (N = 28, 16 males, 12 females; mean age = 20.6 ± 1.4 years). Participants were randomly assigned to a mental fatigue (MF) or control (CON) group and completed baseline and post-condition assessments following a cognitively demanding or neutral task. Repeated sprint performance significantly declined in the MF group, as shown by increased RSA mean time (Δ = 0.432 s, <i>p</i> < 0.001) and total time (Δ = 4.331 s, <i>p</i> < 0.001), with no statistically significant change observed in the CON group. Countermovement jump height remained unaffected; however, repeated jump ability showed impaired contact time (Δ = 0.084 s, <i>p</i> = 0.007) in the MF group. Psychomotor vigilance significantly deteriorated under mental fatigue, as evidenced by slower reaction times (Δ = 119.71 ms, <i>p</i> < 0.001) and increased lapses (Δ = 2.86, <i>p</i> < 0.001). Subjective ratings confirmed elevated perceived exertion (Δ = 0.79, <i>p</i> = 0.002) and mental fatigue (Δ = 8.00, <i>p</i> < 0.001) in the MF group, without changes in motivation. These findings may demonstrate that cognitive fatigue impairs both physical and cognitive performance, even in trained individuals.