Post-exercise metabolic response to acute hypoxic interval bouts

Côté, Danielle (2015) Post-exercise metabolic response to acute hypoxic interval bouts. Masters thesis, Memorial University of Newfoundland.

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Abstract

An overwhelming number of investigations have examined the effect of low arterial partial pressure of oxygen (PₐO₂) on cardiorespiratory response and athletic performance. Less attention has, however, been given to the effect of hypoxic interval exercise on post-exposure substrate oxidation. The study, therefore, examines the effects of hypoxic interval exercise on post-exercise substrate partitioning and energy expenditure. Endurance trained athletes (age: 28±5 yrs; height: 178±7 cm; weight: 75±6 kg; BMI: 24±1 kg•m⁻²) underwent a ramp cycling test in normoxia to determine maximal oxygen uptake (V O₂max: 4.3±0.4 L•min⁻¹) and peak power output (PPO: 331±30 W). Participants were then assigned to a randomized, controlled crossover design experiment consisting of a 45-min basal metabolic rate (BMR), followed by a 60-min cycling interval exercise protocol (3-min @70%PPO, 4.5-min @35%PPO), and a 60-min post-exercise metabolic rate (PEMR). The treatment (hypoxic interval exercise) and the control (normoxic interval exercise) were performed under moderate hypoxic (FiO₂= 0.15) and normoxic (FiO₂= 0.2094) conditions, respectively. To control for the thermic effect of food, the participants consumed a standardized meal (780 Kcal; 26g fat, 98g carbohydrate, and 28g protein) between 18:30 and 19:00 the night before and fasted for 12-hrs prior to exercising. Post-hypoxic interval exercise glucose oxidation significantly decreased by 140±44 mg•min⁻¹ from BMR to PERM while no change was observed post-normoxic interval exercise (2±16 mg•min⁻¹). A corollary of these outcomes resulted in a significant increase in fat oxidation (72±38 mg•min⁻¹) from BMR to PEMR post-hypoxic interval exercise with a non-significant increase post-normoxic interval exercise (14±20 mg•min⁻1). Energy expenditure was not significantly different from BMR to PEMR (0.14±0.22 Kcal•min⁻¹ and 0.03±0.22 Kcal•min⁻¹ in hypoxic and normoxic interval exercises, respectively). In conclusion, hypoxic interval exercise affected substrate partitioning up to one hour after exercising. This result could be explained by higher reliance on endogenous glucose during exercise under hypoxia compared to normoxic condition at the same absolute workload. These results might lead to development of a non-pharmacological approach to weight loss management.

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