EEG–Metabolic Coupling and Time Limit at VO₂max During Constant-Load Exercise

Background: Exercise duration at maximum oxygen uptake ((Formula presented.) O₂max) appears to be influenced not only by metabolic factors but also by the interplay between brain dynamics and ventilatory regulation. This study examined how cortical activity, assessed via electroencephalography (EEG), relates to performance and acute fatigue regulation during a constant-load cycling test. We hypothesized that oscillatory activity in the theta, alpha, and beta bands would be associated with ventilatory coordination and endurance capacity. Methods: Thirty trained participants performed a cycling test to exhaustion at 90% maximal aerobic power. EEG and gas exchange were continuously recorded; ratings of perceived exertion were assessed immediately after exhaustion. Results: Beta power was negatively correlated with time spent at (Formula presented.) O₂max (r = −0.542, p = 0.002). Theta and Alpha power alone showed no direct associations with endurance, but EEG–metabolic ratios revealed significant correlations. Specifically, the time to reach (Formula presented.) O₂max correlated with Alpha/ (Formula presented.) O₂ (p < 0.001), Alpha/ (Formula presented.) CO₂ (p < 0.001), and Beta/ (Formula presented.) CO₂ (p = 0.002). The time spent at (Formula presented.) O₂max correlated with Theta/ (Formula presented.) O₂ (p = 0.002) and Theta/ (Formula presented.) CO₂ (p < 0.001). The time-to-exhaustion was correlated with Theta/ (Formula presented.) CO₂ (p < 0.001) and Alpha/ (Formula presented.) CO₂ (p < 0.001). Conclusions: These findings indicate that cortical oscillations were associated with different aspects of acute fatigue regulation. Beta activity was associated with fatigue-related neural strain, whereas Theta and Alpha bands, when normalized to metabolic load, were consistent with a role in ventilatory coordination and motor control. EEG–metabolic ratios may provide exploratory indicators of brain–metabolism interplay during high-intensity exercise and could help guide future brain-body interactions in endurance performance.