Rapidity of response to hypoxic conditions during exercise.

Abstract

Previous studies have found decreases in arterial oxygen saturation to be linked to reductions in power output (PO). The purpose of this study is to determine how long is required to identify arterial desaturation and change pacing strategy while breathing low oxygen concentrations during simulated competition. We tested the hypothesis that the starting PO of a TT would be the same regardless of inspired F102, due to a strong pretrial template. Trained cyclists performed randomly ordered 3 km time trials with differing patterns of low oxygen administration. The early desaturation time trial began 3 minutes after administration of hypoxic air; the late desaturation time trial began 30 seconds after administration. We saw no early effect on PO when the hypoxic condition was applied prior to the time trial, and there was no difference relative to when hypoxia was applied. The time required to decrease PO was approximately 40 seconds after the start of the trial. Despite reductions in PO, the rating of perceived exertion was greater throughout the hypoxic trial. The results support the strong effect of the pre-exercise template, and the inadequacy of matching PO to perceived exertion during the trial.