Odds are if you are an adult female, then you have taken an oral contraceptive at some point in your life. Many women, athletes included, take oral contraceptives for long periods of time. Could this be affecting athletic performance? A recent study published in the Journal of Strength and Conditioning Research examined the effect of long-term oral contraceptive use on endurance performance in active women.
There were 16 women who participated in the study: 8 women who had used oral contraceptives for an average of 32 months were placed into one group, and the other group consisted of 8 women who were normally menstruating women not using oral contraceptives. Each participant had blood tests performed, and then performed an incremental exercise to exhaustion to find peak VO2 and estimate anaerobic threshold. This test took into account cyclic fluctuations in blood hormone concentrations and took place on the second day of menstruation for women in the group who were not using oral contraceptives, and on the second day after pill cessation in the oral contraceptive group.2
The women in the study also completed a continuous submaximal cycling test that covered three work stages: two 6-minute work stages below anaerobic threshold and one above anaerobic threshold performed to exhaustion. Throughout the tests, pulmonary gas exchange, heart rate, blood pressure, blood lactate concentration, and ratings of perceived exhaustion were measured, and cycling economy was also calculated.3
The results from the study showed similar physical characteristics between both groups. However, peak oxygen uptake and oxygen uptake at the anaerobic threshold were significantly different between the groups. The group not using oral contraceptives was considerably better than the oral contraceptive group. Previous studies have reported significant reductions in peak VO2 after 4-6 months of oral contraceptive use, and this study was consistent with those findings. VO2 was 22% lower in the group using oral contraceptives. Expired minute ventilation, heart rate, blood pressure, and cycling economy for all constant-load work stages were not much different between the groups, and time to exhaustion for severe-intensity cycling was similar as well.4
So what does all of this really mean? The results of this study suggest that long-term oral contraceptive use (longer than 12 months) negatively affects peak VO2 and VO2 at the anaerobic threshold, but despite this reduction, long-term oral contraceptive use does not affect all measures of endurance. Consequently, there is no need for female athletes to be concerned about the effect of long-term oral contraceptive use on endurance performance.
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