Effects of oral contraceptives on peak exercise capacity.

We examined the effects of menstrual cycle phase and oral contraceptive (OC) use on peak oxygen consumption (VO(2 peak)). Six moderately active, eumenorrheic women (25.5 +/- 1.5 yr) were studied before and after 4 mo of OC. Subjects were tested during the follicular and luteal phases before OC and the inactive and high-dose phases after OC. Before OC, there were no significant differences between the follicular and luteal phases in any of the variables studied. There were also no differences between the inactive and high-dose phases. Dietary composition, exercise patterns, and peak heart rate, minute ventilation, and respiratory exchange ratio did not change with OC use. However, OC use significantly (P </= 0.05) increased body weight (59.6 +/- 2.3 to 61.2 +/- 2.6 kg) and fat mass (13.3 +/- 1.3 to 14.5 +/- 1.3 kg) and decreased VO(2 peak) (-11%, 2.53 +/- 0.21 to 2.25 +/- 0.18 l/min). In conclusion, 1) endogenous ovarian steroids have little effect on VO(2 peak), but 2) the exogenous ovarian steroids in OC decrease peak exercise capacity in moderately physically active young women.