Oral Contraceptives and Athletic Performance
Source: Bryner RW, et al. Br J Sports Med 1996;30:36-40.
Bryner et al from the exercise physiology program at the West Virginia University School of Medicine tested 10 women, ages 18-30, for Vo2 max (by a maximal treadmill test) and by an endurance run. The women were randomly assigned to a placebo or low-dose oral contraceptive treatment (1 mg norethindrone and 35 mcg ethinyl estradiol) after first being tested in both the follicular phase and the luteal phase of a menstrual cycle. For comparison, 15 men were studied with the same testing. There were no differences in the men and women between initial and subsequent tests, between the follicular and luteal phases, or during the first and third weeks of treatment with oral contraceptives. Bryner et al conclude that neither menstrual cycle phase nor oral contraceptives affect exercise performance.
Comment by Leon Speroff, MD
Competing athletes are often concerned that oral contraceptives could reduce exercise performance. A rationale for the concern can be traced to the physiologic increase in ventilation during pregnancy, mediated by progesterone. Thus, progestin-enhancement of ventilatory response could consume energy otherwise available for athletic performance. Indeed, previous reports have generated conflicting data measured by laboratory tests. Oral contraceptive use has been reported to decrease maximum oxygen uptake. The value of the current report is that the evaluation involved testing that simulated an athletic event.
Neither progesterone in the luteal phase nor the progestin in the oral contraceptive reduced maximal performance or endurance performance in this study. Previous studies reviewed in the discussion of the above report indicate that progesterone and progestins do stimulate respiration but do not compromise exercise performance. Conflicting data may reflect the large individual variations in conditioning and performance. In the current study, analysis of data in individual subjects failed to demonstrate an effect of menstrual cycle phase or the use of oral contraceptives on performance.
Because athletes are often amenorrheic and hypoestrogenic, oral contraceptives provide not only confidence against the risk of an unwanted pregnancy, but also estrogen support against bone loss. It is now well-recognized that hypoestrogenic endurance athletes experience more stress fractures due to loss of bone. Here is a situation where bone density measurements are worthwhile. A low bone density can help motivate an athlete to take hormone therapy, and a subsequent bone density measurement that reveals a failure of response to estrogen can indicate the presence of a hidden eating disorder.
In view of the above report, oral contraceptives have a lot to offer and no serious drawbacks for the athlete. For the individual who desires amenorrhea and wishes to avoid menstrual bleeding, an effective method is to take the oral contraceptives daily, without a break, thus avoiding withdrawal bleeding.
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