Mental Fatigue Alters Cortical Activation and Psychological Responses, Impairing Performance in a Distance-Based Cycling Trial

Abstract

<b>Purpose:</b> We sought to verify if alterations in prefrontal cortex (PFC) activation and psychological responses would play along with impairments in pacing and performance of mentally fatigued cyclists. <b>Materials and Methods:</b> Eight recreational cyclists performed two preliminary sessions to familiarize them with the rapid visual information processing (RVP) test, psychological scales and 20 km cycling time trial (TT_20km) (session 1), as well as to perform a VO_2MAX test (session 2). Thereafter, they performed a TT_20km either after a RVP test (30 min) or a time-matched rest control session (session 3 and 4 in counterbalanced order). Performance and psychological responses were obtained throughout the TT_20km while PFC electroencephalography (EEG) was obtained at 10 and 20 km of the TT_20km and throughout the RVP test. Increases in EEG theta band power indicated a mental fatigue condition. Repeated-measures mixed models design and <i>post-hoc</i> effect size (ES) were used in comparisons. <b>Results:</b> Cyclists completed the trial ~2.7% slower in mental fatigue (34.3 ± 1.3 min) than in control (33.4 ± 1.1 min, <i>p</i> = 0.02, very large ES), with a lower W_MEAN (224.5 ± 17.9 W vs. 240.2 ± 20.9 W, respectively; <i>p</i> = 0.03; extremely large ES). There was a higher EEG theta band power during RVP test (<i>p</i> = 0.03; extremely large ES), which remained during the TT_20km (<i>p</i> = 0.01; extremely large ES). RPE increased steeper in mental fatigue than in control, together with isolated reductions in motivation at 2th km (<i>p</i> = 0.04; extremely large ES), felt arousal at the 2nd and 4th km (<i>p</i> = 0.01; extremely large ES), and associative thoughts to exercise at the 6th and 16th km (<i>p</i> = 0.02; extremely large ES) of the TT_20km.<b>Conclusions:</b> Mentally fatigued recreational cyclists showed impaired performance, altered PFC activation and faster increase in RPE during a TT_20km.