Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Kinesiology

Supervisor

Dr. Donald H. Paterson

Abstract

This thesis was undertaken to examine the physiological mechanisms that interact to govern the adjustment of O2 uptake (VO2) during the on-transient of moderate-intensity exercise as well as during incremental exercise, using non-invasive measures. Particular emphasis was placed on the information provided by pairing breath-by-breath pulmonary VO2 measures with near-infrared spectroscopy (NIRS)-derived measures to investigate the role of local muscle O2 delivery in the determination of VO2 during various exercise challenges.

The main findings were that: 1) local muscle O2 delivery likely plays a rate-limiting role in the determination of τVO2p (at least when τVO2p is greater than ~20 s), even in young, healthy adults; 2) τVO2p can be reduced by augmenting local muscle O2 delivery (with heavy-intensity ‘priming’ exercise) and increased by impairing local muscle O2 delivery (with acute, mild hypoxia); 3) the relative slowing of the VO2 on-kinetics response when moderate-intensity exercise is initiated from an elevated baseline WR does not appear to be the result of reduced local muscle O2 delivery in older adults; 4) whereas the effects of moderate-intensity work rate (WR) increment were heterogeneous with respect to τVO2p in those with fast versus slow VO2 kinetics, increasing WR increments were associated with increasing O2 costs (i.e., functional gain; G = ΔVO2/ΔWR) regardless of the rate of adjustment; this suggests that τVO2p and functional G may be dissociated; and 5) the appropriateness of a sigmoid regression to characterize the overall Δ[HHb] response to incremental exercise (at least for comparative purposes) was challenged, and a ‘double-linear’ model was proposed as an alternative.

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