Time-course changes in EEG-derived central fatigue during recovery between repeated bouts of exhaustive endurance exercise

Abstract

Background: Endurance exercise performance is determined by fatigue recovery and the maintenance of physiological homeostasis. While previous studies focused on peripheral fatigue, the central nervous system (CNS) regulation, known as central fatigue, is required to understand performance deterioration. Most electroencephalography (EEG) studies use static pre- and post-exercise measurements. This study investigated the time-course changes in EEG-derived central fatigue during repeated bouts of exhaustive endurance exercise and an inter-set recovery period. Methods: Thirteen trained healthy males performed two treadmill running trials to exhaustion at 70% V̇O₂max (EX1 and EX2). A 15-minute recovery period separated the two exercise bouts. During the recovery, participants were randomly assigned to a 3-minute hand immersion in either cold water (10°C; HC) or thermoneutral water (~32°C; Sham). Cortical activity was measured using a 21-channel EEG system. The alpha-to-beta (α/β) ratio was calculated at four specific time points: Baseline, EX1 end, end of Recovery, and EX2 end. Results: The α/β ratio exhibited dynamic temporal patterns across the four measurement time points. Significant differences in the α/β ratio between the Sham and HC conditions were observed in the right hemisphere, specifically at the F4, F8, C4, and P4 electrode sites. Conversely, no significant differences between the conditions were found in the left hemisphere sites, including F3, F7, C3, and P3. Conclusion: Tracking the time-course changes of the EEG α/β ratio provides an objective assessment of dynamic cortical arousal during repeated exhaustive exercise. The application of peripheral hand cooling during the inter-set recovery modulates the progression of central fatigue, with localized responses observed in the right hemisphere.