THE IMPACT
This project identified increased carbohydrate oxidation during exercise matched for absolute intensities in hypoxia compared with normoxia but not during exercise matched for relative intensities. During exercise matched for relative exercise intensities, pre-exercise feeding, and a greater exercise intensity induced an increased reliance on carbohydrate in hypoxia compared with normoxia. Experimental trials showed an increased reliance on fat oxidation in normobaric hypoxia (4300m) compared with normoxia when fasted, with no difference when fed prior to exercise. Thus, pre-exercise feeding is necessary to avoid an over-reliance on the less ‘metabolically efficient’ oxidation of fat during high altitude sojourns.
More advanced stable mass isotope tracer methods utilised at terrestrial altitude showed a reduction in carbohydrate oxidation, derived from muscle, rather than liver glycogen during prolonged exercise in males. However, this response was not replicated in females. Interestingly, a reduction in exogenous carbohydrate oxidation was observed in the females at altitude, demonstrating the need for a sex-specific approach to nutritional strategies at high altitude.
The final study from this project to date demonstrated that carbohydrate supplementation had no effect on substrate oxidation in hypoxia after pre-exercise breakfast consumption. However, an increase in carbohydrate oxidation was observed during exercise (> 60 min) in hypoxia after pre-exercise breakfast omission. This demonstrates that carbohydrate supplementation is likely an efficacious nutritional strategy for individuals in a negative energy balance. This is applicable to populations during chronic exposure to high altitude, as a reduction in energy intake is often induced by appetite suppression in such conditions.
