Effect of Hypoxia on Energy Expenditure During High Intensity Exercise Training

Abstract

Exercising below and above the Maximal Metabolic Steady State (MMSS) induces markedly different physiological responses. This is the only study to date to examine the effect of a well-controlled hypoxic intervention whist controlling for both absolute and relative exercise intensities in normoxia. The purpose of the present study was to (1) examine the energy contribution from different systems during high intensity interval exercise (HIIT) in hypoxia. (2) To investigate whether the same physiological responses of non-steady state (i.e., severe domain) at an intensity that is normally steady state (i.e., heavy domain) in normoxia can be stimulated by introducing hypoxia. It was hypothesized that (1) at an equivalent absolute work rate, exercise in hypoxia will shift energy expenditure (EE) to an increased reliance on anaerobic metabolism relative to normoxia. (2) At an equivalent relative workload, exercise in hypoxia will show similar anaerobic contribution as a percent of total EE. Thereby, hypoxia will shift the exercise intensity from steady state to non-steady state responses yet maintain an equal absolute intensity and mechanical workload. The primary findings of this study demonstrated at an equivalent relative workload, exercise in hypoxia showed similar anaerobic contribution as a percent of total EE to relative intensity exercise in Normoxia. The shift towards anaerobic metabolism in hypoxia was mainly due to increased glycolytic contribution, as opposed to any change in the alactic component. Evidently, in this study Exercise intensity, was the dominant factor that determines metabolic energy requirement, of a given task regardless of the addition of a hypoxic physiological stressor. In conclusion, when HIIT is conducted in hypoxia, a higher relative intensity can be achieved which may be applicable to individuals for whom HIIT is challenging due to pain sensitivity.

Date of Award	2022
Original language	American English
Awarding Institution	HBKU College of Health & Life Sciences