Effects Of Normobaric Hypoxia And Exercise On Cold-induced Vasodilation, Body Temperature, And Oxygen Saturation

Abstract

PURPOSE: The purpose of the current study was to investigate the effects of normobaric hypoxia on the thermoregulatory and the cold-induced vasodilation (CIVD) response before and following submaximal exercise. METHODS: Ten apparently healthy men (23±3 years) volunteered for two experimental trials during which they were exposed to differing O2 saturations (13% O2 and 21% O2) in an environmental chamber. Trials were counterbalanced and blinded from the participant. Following a 60-min acclimation the experimental trials consisted of two 15-min exposures to 5°C water of the non-dominant hand. The exposures were separated by a 30-min bout of submaximal exercise producing the equivalent of 400 watts (W) of metabolic heat. Mean body temperature (MBT), oxygen saturation (SaO2), and thermal sensation (TS) were collected during the final 5 min of each stage. CIVD was measured pre- and post-exercise during each of the cold water exposures on the nailbed of the middle finger on the non-dominant hand. RESULTS: ANOVA revealed a significant time (baseline, acclimation, CIVDpre, exercise, and CIVDpost) by condition (13% O2, 21% O2) interaction for SaO2 (F = 38.4, p < 0.001). Significant differences (p < 0.001) between conditions existed at all time-points with the exception of baseline (p = 1.0). A main effect of time was observed for amplitude temperature (F = 20.034, p < 0.001), which was significantly greater (p < 0.001) at CIVDpost compared to CIVDpre (CIVDpost: 1.13 °C; CIVDpre: 0.28 °C). No significant difference across time or condition exists for MBT or TS. In the 13% O2 condition, the reduction in SaO2 during exercise (81.5%) was positively associated (r = 0.656, p = 0.039) with amplitude temperature at CIVDpost (0.69 °C), which was significantly greater (p < 0.05) compared to CIVDpre (0.14 °C). CONCLUSION: It appears that during rest in normobaric hypoxia, a cold stress test has minimal effect on the CIVD response. During exercise, reduced CIVD amplitude is associated with reduced SaO2. It appears that a submaximal bout of cycling exercise is not the proper stimulus to acutely induce a CIVD response to the magnitude at which physiological changes ensue.