Physiological and cortical determinants of exercise tolerance in sedentary women with obesity

Background: Obesity significantly limits exercise tolerance, yet the specific contributions of central vs. peripheral fatigue remain debated. This study investigated whether early exhaustion in sedentary women with obesity is driven by a failure in central neural drive or by cumulative peripheral physiological strain. Methods: Twelve women with obesity (BMI 35.9 ± 4.0) and ten non-obese controls (BMI 22.3 ± 1.3) performed submaximal cycling at 60% of their maximal aerobic power until voluntary exhaustion. We simultaneously monitored cortical activity via EEG (alpha (α) and beta (β) wave power and the α/β ratio), cardiovascular response (HR), thermoregulation (Tty), and metabolic markers (lactate concentration and body mass loss). Results: Compared with non-obese participants, obese women experienced a significantly shorter exercise duration (∼36.8% lower). This was accompanied by a faster rate of fluid loss (1.2 ± 0.2 vs. 0.6 ± 0.2 kg), a significantly higher peak tympanic temperature (38.1 ± 0.3 vs. 37.7 ± 0.2 °C), and a lower peak heart rate at exhaustion (175.2 ± 5.3 vs. 186.2 ± 6.5 bpm). However, relative intensity reached at exhaustion was similar between groups (93.7 ± 2.9% vs. 96.1 ± 3.3% of HR max, respectively), indicating near-maximal cardiovascular strain in both populations. EEG analyses revealed no significant between-group differences in α activity, β activity, or the α/β ratio across exercise stages. In both groups, α activity decreased and the α/β ratio (index of central fatigue) also decreased from rest to exercise, reflecting increased cortical activation. Conclusion: These findings indicate that early fatigue in sedentary women with obesity is primarily a result of peripheral physiological overload specifically cardiovascular, thermal, and metabolic constraints rather than a lack of central cortical arousal. The similar relative physiological strain at exhaustion suggests that exercise tolerance is limited by reaching critical peripheral thresholds sooner than non-obese counterparts.