A number of recent reports have demonstrated that low volume of high-intensity exercise in the form of sprint interval training (HIIT) can induce substancial improvements in metabolic function and health related outcomes. However, what effect an interval training under hypoxic condition has on post exercise metabolism is still not fully understood.
PURPOSE: To determine the effects of normobaric hypoxia HIIT on substrate partitioning and energy expenditure post-exercise.
METHODS: Nine healthy active male subjects voluntary participate in this study (age:29,6yrs; BMI:24,4). Following a pre trial HIIT familiarization, each participant undertook a fasted state 6x30-s treadmill sprint under simulated altitude normobaric condition (Everest Hypoxic Generator) lowering oxygen saturation (SO2) to 80±5%, with 3min recovery between each sprint. Gas analyses were done before exercise (fasted state), 45min post exercise (45min post) and 150min post exercise (150min post) to calculate and compare RER, Caloric Expenditure and Fat Oxidation.
RESULTS: RER was reduced by 12% and 4%, compared to the fasted state, at 45min post and 150min post, respectively (p<0,05 only for 45min post). Total energy expenditure was increased by 5% at 45min post exercise (NS), and did not differ compared to the fasted state. Fat oxidation was increased by 67% and 17% at 45min and 150min post exercise, respectively (p<0,05 for both) with a concomitant reduction in carbohydrate oxidation (p<0.05 for both).
CONCLUSION: HIIT performed under hypoxic condition induces a transient reduction of post-exercise RER, associated with a shift in substrate partitioning, towards lipid sources, compared to pre-exercise metabolism.