End-tidal carbon dioxide and oxygen tension, carbon dioxide production (VcoJ, oxygen consumption (VoJ, minute ventilation (Ve), tidal volume, and respiratory rate were measured continuously throughout exercise. Air flow and gas measurements were corrected for ambient temperature, barometric pressure, water vapor, and expressed in body temperature pressure saturated (BTPS). Peak exercise values of Vo2 were expressed as percent of predicted maximum, and Ve as percentage of estimated maximum voluntary ventilation. birth control yasmin
The anaerobic threshold (AT) was deterj mined noninvasively as the point at which (1) Ve rose out of proportion to Vo2, (2) the respiratory quotient rose above 1.0, and (3) the ventilatory equivalent for oxygen rose out of proportion to that of COa during submaximal exercise. It was expressed in liters per minute Vo2 and as percent predicted maximum Vo2. Values of AT less than 40 percent predicted maximum Vo2 were considered abnormally low. The linear increase in HR with Vo2 was used to construct a regression equation for each subject to obtain a slope of the HR response (SHR) as suggested by Jones et al. The linear increase in minute ventilation with Vco2 below the AT was used to construct a regression equation for each subject to obtain a slope (SVe).