Acute Normobaric Hypoxia Exposure and Excess Post-Exercise Oxygen Consumption

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Aerospace Medicine and Human Performance





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BACKGROUND: Excess postexercise oxygen consumption (EPOC) is an elevation in oxygen consumption ((V) over doto(2))) 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 (V) over doto(2) 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 x 3 repeated measures ANOVA. RESULTS: No sex differences were detected for any variable. EPOC duration increased significantly at each simulated altitude increase (CON = 15/ +/- 1.9 vs. HI = 20.7 17 min) (HI vs. EXT - 28.1 +/- 2.6 min). Likewise, EPOC magnitude increased significantly at each simulated altitude (CON - 73.5 4 9.9 vs. HI - 99.1 +/- 93 ml O-2) (HI vs. EXT = 139.7 +/- 14.3 ml O-2). 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.


Simulated altitude; Aerobic exercise; Magnitude; Metabolic response


Medicine and Health Sciences



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