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Effects of oral contraceptives on peak exercise capacity
Gretchen A. Casazza, Sang-Hoon Suh, Benjamin F. Miller, Franco M. Navazio, and George A. Brooks
Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California 94720
We examined the effects of menstrual cycle phase and oral contraceptive (OC) use on peak oxygen consumption (O2 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 O2 peak (11%, 2.53 ± 0.21 to 2.25 ± 0.18 l/min). In conclusion, 1) endogenous ovarian steroids have little effect on O2 peak, but 2) the exogenous ovarian steroids in OC decrease peak exercise capacity in moderately physically active young women.
While I used to think that a low dose OC would keep estrogen levels down, between this paper and another it referenced (See Thong et al., JAP 88: 2037-2044, 2000) it appears that OCs containing 30 - 35 ug of ethinyl estradiol, while supressing endogenous estrogen throughout the cycle, results in circulating estradiol concentrations of nearly 400pg/ml which are bumping the early pregnancy range and we know that partitions food toward fat.
Food for thought.
W6
Gretchen A. Casazza, Sang-Hoon Suh, Benjamin F. Miller, Franco M. Navazio, and George A. Brooks
Exercise Physiology Laboratory, Department of Integrative Biology, University of California, Berkeley, California 94720
We examined the effects of menstrual cycle phase and oral contraceptive (OC) use on peak oxygen consumption (O2 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 O2 peak (11%, 2.53 ± 0.21 to 2.25 ± 0.18 l/min). In conclusion, 1) endogenous ovarian steroids have little effect on O2 peak, but 2) the exogenous ovarian steroids in OC decrease peak exercise capacity in moderately physically active young women.
While I used to think that a low dose OC would keep estrogen levels down, between this paper and another it referenced (See Thong et al., JAP 88: 2037-2044, 2000) it appears that OCs containing 30 - 35 ug of ethinyl estradiol, while supressing endogenous estrogen throughout the cycle, results in circulating estradiol concentrations of nearly 400pg/ml which are bumping the early pregnancy range and we know that partitions food toward fat.
Food for thought.
W6
