Oxygen Uptake Kinetics during Exercise

This thesis has investigated oxygen uptake ( i r02) kinetic regulation during whole body exercise by investigating not only the breath-by-breath V O ~ response to a change in work rate but also incorporating an examination of data analysis processes and simulation of a physiological V O ~ model. Five experiments have been completed to answer the following questions: Experiment 1: What effects do sample duration, ensembling, interpolation, and smoothing have on time constant determination? Experiment 2: Is the slope of the V O ~ response to a ramp work rate altered by changing the inspired fraction of oxygen? Experiment 3: Does glycogen depletion acutely reduce the rate of carbohydrate utilization and thus quicken the VO;? time constant? Experiment 4: Does one-legged training alter the h2 time constant of the trained and the untrained leg differently? Experiment 5: With respect to the muscle 6 7 0 ~ time constant, does expansion of an accepted physiological model of oxygen uptake to include a heterogeneous muscle compartment significantly alter modeled V% kinetics? Experiment 1 demonstrated that a more accurate ?oz time constant estimation from a step increase in work rate can be acquired by artificially extending the steady state portion of the vo2 response. Experiment 2 showed that, above the anaerobic threshold, the A ~ O ~ A W R relation, relative to nornloxia, is increased in hyperoxia and decreased in hypoxia. This suggests that a change in AVWAWR above the anaerobic threshold is related to the recruitment pattern of muscle units and their kinetic characteristics rather than simply the onset of anaerobiosis. In experiment 3 there was no difference in the V O ~ kinetic response of the glycogen-depleted state compared with a normal glycogen state. This indicates that rleither the physiological nor biochemical changes induced by glycogen depletion 3nected ?02 kinetics. The trained leg in experiment 4 had a faster V O ~ response than the untrained leg. A simple conclusion from this is that V O ~ kinetics are