Effects on Oxygen Consumption and Metabolic Gene Expression when Determining Experimental Exercise Intensity Based on Exercise Capacity Tests Conducted in Hypoxic and Normoxic Environments

Abstract: Exercise intensity can be set relative to VO2 max measured during hypoxic or control conditions in studies investigating exercise in hypoxic environments. It currently is not clear which is the most appropriate method. Objective: The objective of this brief report is to determine the response to 1 hour of cycling at 60% of peak power when measured in either normoxic or hypoxic conditions. Methods: Eleven recreationally active male participants (24 ± 4 yrs, 173 ± 20 cm, 82 ± 12 kg, 15.2 ± 7.1% fat, 4.0 ± 0.6 L x min-1 VO2 max) completed two 1 hour cycling exercise trials at 60% of peak power followed by 4 hours of recovery in ambient environmental conditions (975 m) and at normobaric hypoxic conditions simulating 3000 m in a randomized counter balanced order. Results: VO2 max was not different between trials in relative (p=0.272) or absolute terms (p=0.105) but peak power at VO2 max was higher in the 975 m trial (288 ± 17 watts) than the 3000 m trial (262 ± 12 watts, p=0.003) corresponding to differences at 60% of VO2 max power. Gene expression of HIF-1α, COX, PGC-1α, HK, and PFK increased with exercise (p\u3c0.05) but did not differ between trials. There was a trend (p=0.072) toward increased muscle glycogen use in 975m. Conclusions: Although there were not statistical differences for muscle markers in the current study, these data should be considered when determining exercise intensity in hypoxia related research