The purpose of this study is to develop a single, standardized test to determine how individuals tolerate acute hypoxia in a stepwise fashion. We aim to evaluate the association between multiple factors, such as ventilatory compensation, heart rate response, acid-base changes, sex, pulmonary function, etc, which may explain why some individuals tolerate exercise in hypoxia better than others. Identifying these factors of association will inform future pharmacological and non-pharmacological attempts to combat acute hypoxic exercise.