The effect of Aerobic Conditioning on Cardiovascular and Respiratory Recovery in Normobaric Hypoxia

Abstract

PURPOSE: The purpose of this study was to determine differences in post-exercise oxygen consumption, cerebral oxygenation, heart rate (HR), minute ventilation (VE), between aerobically fit and unfit young males acutely following exercise in hypoxia compared to normoxia. METHODS: Apparently healthy college age males took part in two trials consisting of normobaric normoxia (21% oxygen) and normobaric hypoxia (12% oxygen). Fit (n = 3; VO2max = 51.5 ml • kg-1 • min-1 ± 3.1) and unfit (n = 3; VO2max = 34.4 ml kg-1 min-1 ± 5.6) males cycled at 50% of altitude adjusted VO2max (-26% of normoxic VO2max) for 1-hr after a 2-hr baseline. Data was collected at baseline, 5 min prior to the end of exercise and again at 5 and 60 min after the end of exercise. RESULTS: An interaction effect (trial x time x fitness) revealed significance in the change of cerebral oxygenation over the course of the recovery period. In fact, the unfit group demonstrated a significantly smaller change (P <0.05) change in cerebral oxygenation immediately post-exercise (-4.3% ± 2.2) compared to fit individuals (-22.0% ± 2.6). Change in cerebral oxygenation at the same time point during the normoxic trial was not significantly different (Fit = 10.7% ± 5.9, Unfit = 5.7% ± 2.6; P > 0.05). In addition, percent change of O2 consumption post-exercise (compared to baseline) was significantly greater in the unfit group in the hypoxic trial (Unfit = 121.1% ± 4.0, Fit = 70.1% ± 16.3; P < 0.05), but no significant difference was demonstrated during the normoxic trial. VE and HR were significantly different between the trials in all subjects but not between groups (P < 0.05). VE was greater during hypoxia (P < 0.05) in all subjects while the fit group demonstrated a significantly higher VE during exercise in hypoxia (P < 0.05) compared to unfit individuals. CONCLUSIONS: The data suggests that when exposed to hypoxia aerobic conditioning may have an affect on acute recovery responses to exercise in hypoxia. Future research may examine changes in the recovery response to exercise after acclimatization to hypoxic environments.