Guest blog by Kirsty Elliott-Sale
Oral contraceptive pills are used by women, including elite athletes, around the world. In the UK they are the most common type of hormonal contraceptive used by elite sportswomen (1). Oral contraceptives are designed to prevent pregnancy, but they are also used by some athletes to manipulate their menstrual cycle, so they can control the timing of, or eliminate entirely, their periods (2). (read more on the effect of menstrual cycle on performance here) Some sportswomen find having periods inconvenient, being an extra concern during training or competition, and some experience negative side-effects from their periods, which could adversely affect their performance.
Some sportswomen find having periods inconvenient, being an extra concern during training or competition, and some experience negative side-effects from their periods, which could adversely affect their performance.
How do oral contraceptives work?
The most popular kind of oral contraceptive has a 28 day cycle and is taken in a 21:7 routine. This means that one pill is taken every day for 21 continuous days, followed by 7 pill-free days. Oral contraceptives have two concurrent physiological consequences: (i) they reduce the amount of natural oestrogen and progesterone in the body throughout the 28 day cycle and (ii) they provide an artificial oestrogen and progestin into the body during the 21 pill taking days.
Effects of oral contraceptives on performance
We investigated whether these two coexisting hormonal profiles affect exercise performance by examining previous studies in this area. Our investigation involved finding and analysing studies that looked at oral contraceptive pill-taking versus pill-free days and by comparing oral contraceptive users to naturally menstruating women. We also examined the quality of the studies we identified, so we could rate our confidence in the evidence; i.e., high quality studies provide high quality evidence, giving us a greater degree of confidence in the findings and vice versa. Our investigation uncovered 42 studies that were relevant to our questions and all together these studies included 590 participants. Most studies (83%) were graded as moderate, low or very low quality, and only 17% achieved high quality status.
This means that from a practical perspective, we don’t need to make special exercise guidelines for sportswomen using oral contraceptives.
What did we find?
Our results showed that on average oral contraceptives might result in slightly poorer exercise performance when compared to naturally menstruating women who don’t take an oral contraceptive. It is very important to note though that if you try to apply this concept to a group of sportswomen, the size of this effect (how much influence it will have) will likely be trivial. Effect sizes are on a scale starting with trivial, followed by small, then medium, then large, meaning that the effect size of oral contraceptives on exercise performance is less than small. This means that from a practical perspective, we don’t need to make special exercise guidelines for sportswomen using oral contraceptives.
Take an individual athlete approach to oral contraceptive pill use. Focus on each athlete’s response to their oral contraceptive, as some athletes may be affected, and some may not be.
Practical implications
In addition to the effect of oral contraceptive pill use on exercise performance being less than small, the results of individual studies were very variable making it difficult to draw a consistent conclusion. This means that you are better to take an individual athlete approach to oral contraceptive pill use, focusing on each athlete’s response to their oral contraceptive, as some athletes may be affected, and some may not be. Our investigation also showed that exercise performance did not change between the pill taking and pill free days, meaning that sportswomen do not need to worry about which day of their oral contraceptive pill cycle they are on when thinking about their performance.
To upgrade our confidence in our findings we repeated our analyses on only the moderate and high quality papers and the results were the same, meaning that we have good confidence in our results and conclusion.
... sportswomen do not need to worry about which day of their oral contraceptive pill cycle they are on when thinking about their performance.
Take home messages
Our overall take home messages are: (i) some oral contraceptive using sportswomen might have a very small decline in performance compared to naturally menstruating, non-oral contraceptive using sportswomen, but this is best considered at an individual level rather than applying this finding to groups of sportswomen, and (ii) there appears to be no performance related evidence to warrant general guidance on oral contraceptive pill taking days versus pill free days.
References
Martin D, Sale C, Cooper SB, Elliott-Sale KJ. Period prevalence and perceived side effects of hormonal contraceptive use and the menstrual cycle in elite athletes. Int J Sports Physiol Perform. 2018;13(7):926–32.
Schaumberg MA, Emmerton LM, Jenkins DG, Burton NW, de Jonge XAJ, Skinner TL. Oral contraceptive use for manipulation of menstruation in young, physically-active women. Int J Sports Physiol Perform. 2017;16(1):e68–e6969.
Elliott-Sale, K.J., McNulty, K.L., Ansdell, P. et al. The Effects of Oral Contraceptives on Exercise Performance in Women: A Systematic Review and Meta-analysis. Sports Med (2020). https://doi.org/10.1007/s40279-020-01317-5
