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

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.

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).

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.

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.