Carbon Dioxide Expiration and Performance Fatigability Following Aerobic Exercise Training: A Longitudinal, Observational, Pilot Study

Purpose: This study examined the influence of aerobic exercise training (AET) on components of carbon dioxide expiration (VCO₂), cardiorespiratory function, and fatigability.

Methods: Twenty healthy adults completed peak cardiopulmonary exercise (CPX) and submaximal tests before and after a vigorous, 4-week AET regimen. Each test was followed by a 10-min recovery and endurance test at 70% of peak wattage attained during CPX. Fatigability was assessed using testing durations and power output. Respiratory buffering (excess VCO₂) and non-buffering (metabolic VCO₂) were calculated. Data were analyzed for significance (p<0.05) using regressions and paired t-tests.

Results: Significant improvements in all measures of fatigability were observed after AET. A significant increase in excess VCO₂ was observed, though not in metabolic VCO₂. Excess VCO₂ was strongly predictive of fatigability measures.

Conclusion: Significant decreases in fatigability are often observed in clinical populations such as obstructive or restrictive lung disease or pulmonary hypertension following AET, even when peak cardiorespiratory function does not appear to adapt. Decreases in fatigability appear to predict longevity with no yet identified mechanism. These results suggest that respiratory buffering and metabolic components of VCO₂ may adapt independently to AET, introducing foundational plausibility for an influence of respiratory buffering adaptation to AET on fatigability status.