Cardiorespiratory dynamics: sensitivity of the on-transition to endurance-training status

Abstract

This project investigated the sensitivity of oxygen uptake (V˙O₂) dynamics to training-induced physiological changes, across a broad spectrum of endurance-training histories. Forty subjects participated: sedentary (n = 10), active healthy (n = 10), regular runners (n = 10), and competitive distance runners (n = 10). Subjects completed a cycle step-function protocol, to elicit a steady state at 60% maximal work rate. Breath-by-breath data were collected for V˙O₂ and cardiac frequency (ƒ_c), and modelled mathematically, and used to determine the average response times to attain 20%, 40%, 60%, 80% and 100% of the respective steady states. The between-group comparisons for both V˙O₂ and ƒ_c revealed significantly faster response times to 40%, 60%, 80% and 100% of the induced response, for the better trained subjects (P < 0.05). In general, this technique permitted differentiation between the V˙O₂ and ƒ_c response dynamics of non-elite subjects from a broad range of endurance-training histories, with differences becoming more pronounced as subjects approached the steady state.