Acute Normobaric Hypoxia Exposure and Excess Post-Exercise Oxygen Consumption

BACKGROUND: Excess postexercise oxygen consumption (EPOC) is an elevation in oxygen consumption (Vo₂) following exercise. Altitude decreases maximal oxygen uptake; however, studies are equivocal concerning the effect on resting metabolic rate. The EPOC response has not been studied with normobaric hypoxia. The purpose was to observe EPOC following constant-load cycling in normobaric hypoxia.METHODS: Subjects (N = 7 women, 7 men) completed resting metabolic rate testing between 06:00 and 08:30. Constant workload cycle exercise was performed (10 min at 100 W) while breathing air from an altitude simulator under the following conditions: normoxic control (CON), 3353 m (11,001 ft; HI), and 6401 m (21,001 ft; EXT). Subjects completed remaining conditions in a counterbalanced order. Upon completion, participants were reconnected to the metabolic system until a running 5-min average of Vo₂ values returned to baseline (EPOC duration). Magnitude was determined by summing the net oxygen consumption each minute during the EPOC period. Data were analyzed using 2 × 3 repeated measures ANOVA.RESULTS: No sex differences were detected for any variable. EPOC duration increased significantly at each simulated altitude increase (CON = 15.2 ± 1.9 vs. HI = 20.7 ± 1.7 min) (HI vs. EXT = 28.1 ± 2.6 min). Likewise, EPOC magnitude increased significantly at each simulated altitude (CON = 73.5 ± 9.9 vs. HI = 99.1 ± 9.3 ml O₂) (HI vs. EXT = 139.7 ± 14.3 ml O₂).DISCUSSION: The EPOC response to simulated altitude represents elevated caloric expenditure that must be accounted for. Individuals who are active at altitude must consider the increased caloric deficit despite a loss of appetite that is common with altitude exposure.Navalta JW, Tanner EA, Bodell NG. .