Role of Respiratory Buffering in the Relationship Between Recovery and Performance Fatigability After Aerobic Exercise Training

Purpose: This study characterized the influence of excess expired carbon dioxide (excess V̇ co 2 ) in the relationship between recovery and fatigability. Methods: Twenty healthy adults completed peak cardiopulmonary exercise tests (CPXs) and constant work rate tests before and after a vigorous, 4-week aerobic exercise training (AET) regimen. Each test was followed by 10 minutes of recovery and an endurance test at 70% of peak watts attained during CPX. Fatigability was assessed by measures of time to exhaustion and power output. Metabolic and recovery capacity indices were obtained. Data were analyzed using correlations and regressions and compared pre/post AET using paired t tests. Results: Significant improvements in recovery and fatigability were observed after AET, along with significant increases in total and excess V̇ co 2 . Relationships between measures of recovery and fatigability were observed, although strengths of the relationships were diminished after controlling analyses for the effect of excess V̇ co 2 . Conclusions: This study suggests that the ionic buffering capacity may moderate the relationship between recovery and fatigability. These results could have implications regarding AET-induced buffering dynamics, and its role in fatigue resistance when performing activities above moderate intensities. This may be of particular importance in patients with cardiopulmonary complications, unable to improve peak aerobic capacity.