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.

Keywords: Fatigue; Pacing; Placebo; RPE; Supplementation.