Thechangesincardiorespiratoryvariables,relatedtotheircorrespondingrestinglevels,duringthe2minperiodofunloadedcycling exerciseinthefourgroups.Normoxemicandhypoxemicsubjectsareidentifiedbyblackandopensymbols,respectively.Uptodown:heart rate (HR), minute ventilation (VE), respiratory frequency (fR), and tidal volume (VT). Values are mean ± SEM. Asterisks denote the first significantchange(∗