Absolute and relative work capacity in women at 758, 586, and 523 torr barometric pressure

Six young women performed an incremental bicycle work test at sea level barometric pressure (PB = 758 torr) and during acute exposure (1 h) to simulated altitudes of PB 586 and 523 torr. Submaximal oxygen uptake (VO2) for a given workload was independent of altitude but maximal oxygen uptake (VO2 max) decreased 10 and 13%, respectively, at the higher altitudes. Although heart rate (fC) was consistently higher at altitude for a given VO2, the slope of fC vs, VO2 was independent of altitude and VO2 max. Exercise fC appeared to be a function of the relative workload i.e. VO2 as a percentage of VO2 max measured at each PB. Carbon dioxide (CO2) elimination increased with altitude for a given VO2 but also was a function of the relative workload. Pulmonary ventilation (BTPS), however, was consistently 10-15% higher at altitude when expressed as a percent of VO2 max, primarily due to an increase in respiratory rate. Compared to published studies on males, this increased ventilation may impart a slight advantage to women in maintaining arterial oxygenation, but ventilatory reserve may be decreased and limited at higher altitudes. At altitudes down to PB 523 torr, the control of fC responses and decrements in maximal oxygen uptake in women were similar to males, but ventilatory control mechanisms differed.