Total Expired Non‐Metabolic VCO2 and VCO2 Recovery Kinetics as Predictors of Performance Fatigability During Exercise

Abstract

PurposeThe severity of performance fatigability (PF) and the capacity to recover from activity are each profoundly influenced by skeletal muscle energetics, specifically the ability to buffer fatigue‐inducing ions produced as a result of anaerobic metabolism. The mechanisms responsible for buffering these ions results in the production of non‐metabolic carbon dioxide (CO2) that can be measured as expired CO2 (VCO2) during cardiopulmonary exercise testing (CPET). Yet, the relationships between PF and both total expired non‐metabolic (NMVCO2) and the capacity to recover from activity have yet to be investigated.Methods7 healthy subjects (30.71 ± 5.12 years) completed both a maximal and submaximal CPET on separate days, each followed by a 10‐minute recovery and 10‐minute walk test. Oxygen consumption (VO2) and VCO2 on and off‐kinetics (transition constant‐Kt and oxidative response index‐ORI), NMVCO2, and PF severity scores were measured. Data were analyzed using Pearson's correlations and regression analyses. Statistical significance was set at p<0.05.ResultsNMVCO2 accumulation and VCO2 off‐kinetic ORI accounted for 93% of the variance of PF severity scores (r2 = 0.932; p = 0.012). Measures of VCO2 off‐kinetics following both maximal (ORI r2 = 0.932, p < 0.001; Kt r2 = 0.919, p < 0.001) and submaximal (ORI r2 = 0.928, p < 0.001; Kt r2 = 0.955, p < 0.001 ) CPET and NMVCO2 (r2 = 0.614, p = 0.0371) were better predictors of PF than traditional measures of VO2 (VO2 peak r2 = 0.388, p = 0.135; AT‐VO2 r2 = 0.297, p = 0.206).ConclusionPrevious studies investigating relationships between cardiopulmonary variables and PF have traditionally utilized measures of VO2. The current study demonstrates that measures of VCO2 may be more predictive of PF and its clinical manifestations. Furthermore, these measures were able to better predict PF even following submaximal testing presenting a less strenuous clinical measure of PF for those populations in which maximal exercise testing may be contraindicated.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.