This project aims to investigate cerebral deoxygenation during exercise in hypoxia in order to highlight a potential association with acute mountain sickness susceptibility. Although studies report cerebral blood flow as contributor to AMS insurgence, to date non study has provided evidence in monitoring cerebral deoxygenation during exercise in hypoxia. We hypothesize that subjects with higher levels of cerebral deoxygenation during exercise in hypoxia will be more prone to develop AMS.