METABOLIC DEMAND DRIVES THE OXYGEN UPTAKE KINETICS DURING THE EARLY STAGES OF INTENSE WORK

Sylvester, J. L., Burdette, S. D., Cross, S. W., Idemudia, N. O., Curtis, J. H., Vingre, J. L., & Hill, D. W. (2012). The effect of work rate on oxygen uptake kinetics during exhaustive severe intensity cycling exercise. Presentation 2208 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

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During exhaustive severe intensity exercise, the oxygen uptake increases exponentially, with a time constant of ~30 seconds. After approximately one to two minutes, a slow-component emerges and drives oxygen uptake to its maximum. There are clear differences in the oxygen-uptake response profile across exercise intensity domains. These disparities might not be attributable to metabolic demand but, rather, to characteristics of the various intensity domains, such as the consequences of lactic acid production.

This study investigated the role of exercise intensity on the oxygen uptake response profile at intensities wholly within the severe domain in mixed-gender Ss (M = 8; F = 4). Ss performed exhaustive constant-power cycle ergometer tests at two different severe intensity work rates (263 78 W and 214 64 W). Smoothed breath-by-breath oxygen uptake data were fitted to a two-component (primary response and slow-component) model using iterative regression.

Times to exhaustion were 217 27 seconds and 590 82 seconds, respectively. The VO2max values were similar at the two different work rates. The amplitude of the primary response was greater at the higher work rate than at the lower work rate. The amplitude of the slow-component was smaller. Additionally, the time delay before the emergence of the slow-component was shorter at the higher work rate.

Implication. Exercise intensity affects the oxygen uptake response profile within the severe intensity work domain. It is suggested that metabolic demand drives the primary response of oxygen uptake kinetics within this severe work-intensity domain.

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