Non-metabolic VCO 2, Recovery Off-kinetics, And Performance Fatigability Following Chronic Exercise

Abstract

PURPOSE: This study characterized the role of non-metabolic expired carbon dioxide (nm-VCO2) in the relationship between recovery and performance fatigability (PF). METHODS: Twenty adults (men, n=9, age=44.7±13.9 years; women, n=11, age=50.3±11.1 years) completed peak cardiopulmonary exercise tests (CPET) and submaximal constant work rate tests (CWRT) on the cycle ergometer on separate days before and after a vigorous, 4-week aerobic exercise training (AET) regimen. Each test was followed by a 10-minute passive recovery and endurance test at 70% of peak watts attained during CPET. PF was indexed by endurance test duration following both peak CPET (End1) and CWRT (End2), peak CPET time (pk-Time) and watts (pk-Watts). Metabolic indices were total VCO2 (tVCO2), metabolic VCO2 (m-VCO2), nm-VCO2, and recovery VO2 and VCO2 off-kinetics response indices (ORI). Data were analyzed using paired t-tests and correlations and compared before and after AET. RESULTS: Significant improvements in recovery and PF measures were observed after AET, along with significant increases in tVCO2 and nm-VCO2. No significant change in m-VCO2 was observed.Relationships between measures of recovery and PF were observed, though the strength of the relationships were diminished (pk-Time, pk-Watts) or became non-significant (End1, End2) after controlling analyses for the effect of nm-VCO2.CONCLUSION: The current study suggests nm-VCO2 may moderate the relationship between recovery and PF and may have implications regarding AET induced buffering dynamics and its role in fatigue resistance during activity above moderate intensities.