The primary purpose of the study was to investigate effects of an orally administered ketone ester drink on endurance exercise performance during acute extreme hypoxia. Drinking this ketone supplement increases energy substrates known as ketone bodies in the blood, which may also act as metabolic signaling molecules. The ketone drink used in this study is recognized by the FDA as generally regarded as safe (GRAS). Some reports suggest that high ketone levels may enhance one's ability to tolerate hypoxia.

High altitude environments limit oxygen availability in circulation and working tissues, leading to a decreased physiological reserve during physical exertion. Acute hypoxia elevates heart rate during submaximal work in a compensatory attempt, but decreases maximal heart rate progressively with increasing hypoxia. This contributes to a reduction in aerobic power (i.e. maximal rate of oxygen uptake, VO2max) an average of 6.3% per 1000m of elevation. Consumption of exogenous ketone bodies has been shown to enhance oxygen availability at rest at simulated altitudes up to 6100m, associated with better cognitive performance.

Inclusion Criteria:

• Healthy adult males 18 years of age or older (females are excluded because the 7th SFG consists only of males)
• Able to provide informed consent
• Able to perform the prescribed exercise and all study assessments
• Proficiency with the English language (reading, writing, speaking)

Exclusion Criteria:

• Any health or medical condition (e.g., cardiovascular, respiratory, musculoskeletal, neurologic) that would preclude exercise testing or potentially influence exercise performance, as determined by health and medical history questionnaire.
• Any condition that would preclude an accurate DXA body composition scan (e.g. joint replacement).

All data will be immediately de-identified and shared with participants.

Participants are blinded to ketone or placebo consumption.