Traditional Central and Peripheral Physiologic Adaptations not Required to Improve Fatigability and Recovery in Response to a Vigorous Aerobic Exercise Regimen

Abstract

Purpose : This study assessed relationships between cardiovascular (CV) function, oxygen extraction, respiratory buffering, performance fatigability, and recovery capacity in response to chronic exercise perturbation. Methods : 16 healthy men (n=6, age=39.5±14.3) and women (n=10, age=50.0±11.7) completed peak cardiopulmonary exercise testing (CPET) followed by 10 minutes of passive recovery before and after a vigorous, 4-week aerobic exercise cycling training regimen. Primary measures of interest include CV function (cardiac output: Q, stroke volume: SV), oxygen extraction (arteriovenous oxygen difference: a-vO2 diff), respiratory buffering (excess VCO2), performance fatigability (pk-Time), and recovery (VO2 oxidative response index/ORI). Data were analyzed for significant (p<0.05) changes using paired t-tests and associations between variables were assessed using correlations (r2). Results : Significant increases in excess VCO2 (0.58L, p=0.003) and pk-Time (66sec, p<0.001), as well as improvements in recovery (VO2-off ORI 8.7ml/s, p=0.001) were found following training. No significant increases were found in Q (0.413 l/min, p=0.827), SV (3.07 ml; p=0.717) or a-vO2 diff (7.41 l/min, p=0.420). Q was significantly associated with pk-Time (r2=0.433, p=0.013) and VO2-off ORI (r2=0.506, p=0.003) and excess VCO2 was significantly associated with pk-Time (r2=0.848, p<0.001) and VO2-off ORI (r2=0.819, p<0.001), while a-vO2 difference was not significantly correlated with any of these measures. Conclusion : In the current study, measures of performance fatigability and recovery changed significantly, while measures of cardiac function and oxygen extraction did not significantly improve, in response to a 4-week, high-intensity cycling protocol. Furthermore, measures of respiratory buffering both increased following training and demonstrated strong relationships with performance fatigability and recovery. These findings suggest that traditional central and peripheral adaptations may not be required to decrease performance fatigability and improve recovery indicators, while non-traditional measures of respiratory buffering may play a vital role, recognizing that such adaptations and relationships may be protocol dependent.