Caffeine improved cycling trial performance in mentally fatigued cyclists, regardless of alterations in prefrontal cortex activation

Abstract Purpose To verify whether caffeine (CAF) could increase the prefrontal cortex (PFC) activation and improve 20 km cycling time trial (TT 20km ) performance in mentally fatigued cyclists. Methods After preliminary TT 20km , twelve recreational cyclists (VO 2MAX of 58.9 ± 6.2 mL kg min −1 ) performed a familiarization with a cognitive test to induce mental fatigue (MF) and psychological scales. Thereafter, they performed: 2) a baseline TT 20km ; 3) a mentally fatigued TT 20km (MF); 4 and 5) a mentally fatigued TT 20km after CAF (MF + CAF) or placebo (MF + PLA) ingestion, in a double-blind, counterbalanced design. Performance and psychological responses were obtained throughout the TT 20km , while PFC electroencephalography (EEG) theta wave was obtained before and after the mental fatigue test. Results The mental fatigue-induced increase in EEG theta wave (↑ ~ 4.8%) was reverted with CAF (↓ 8.8%) and PLA ingestion (↓ 4.8%). CAF improved TT 20km performance in mentally fatigued cyclists by reducing time ( p  = .00; ↓ ~ 1.7%) and increasing W MEAN (p = .00; ↑ ~ 3.6%), when compared to MF + PLA. The RPE-power output ratio was lower ( p  = .01), but affect ( p  = .018), motivation ( p  = .033) and emotional arousal ( p  = .001) were greater throughout the TT 20km in MF + CAF than in MF + PLA. Conclusions CAF ingestion improved TT 20km performance and psychological responses in mentally fatigued cyclists, despite the unaltered PFC activation.