Her Active Life

Click here for the Lead Stories

The Menstrual Cycle, Oral Contraceptives and Athletic Performance:  How Are They Related?

Posted August 10, 2007 at 06:00 PM by Bridget Sullivan

Section: Her Fitness, Her Health, Her News, Special Features

The following article was submitted by A.J. Melnikas.  A.J. Melnikas currently works in clinical research.  In the past, she has worked with non-profit health organizations targeting women’s and adolescent health issues. She will begin MPH studies this fall. An avid runner and coach, A.J. has completed 4 marathons and is planning to run Boston next year. Her cultural adventures include studying in Spain, South Africa and Nepal; teaching English in China and traveling to France, Belize, Japan, Swaziland and the Dominican Republic.

How do birth control pills affect athletic performance? Is a certain time in the menstrual cycle better for optimal athletic performance? These are questions many female athletes ask, especially when they start or change oral contraceptive pills (OCPs).

There have been a number of studies examining how the menstrual cycle affects female athletes, and whether different parts of the cycle are better or worse for strenuous exercise. However, studies of female athletes taking OCPs are less common. Some studies have examined knee injuries and bone density in athletes taking birth control. Additionally, recent research has examined oral contraceptives and the effects on hydration in endurance athletes. Many of these studies have shown minimal effects on performance and most women should not notice a significant change in performance while taking OCPs. Some studies even suggest that the menstrual cycle has no effect. However, it is important to note that researchers continue to study female hormones, OCPs and their effect on athletic performance and there are some things you may want to consider before starting the pill and/or planning your next race.

You may be aware that the menstrual cycle is defined by different phases occurring in (approximately) a 28-day period. For more information about the different phases see www.knowmycycle.com. One study on athletic performance compared athletes in follicular phase (first day of menstruation until ovulation) and the luteal phase (ovulation until first day of menstruation). Very little change was found in most measures, but VO2 max was slightly decreased in the luteal phase. VO2 max is a measure that examines the body’s ability to carry and utilize oxygen during exercise. 

A decrease in VO2 max may mean a decrease in performance in endurance athletes, though as this study pointed out the difference may not be significant in all female athletes. This study did not examine the difference between athletes using OCP and those not. Although you shouldn’t avoid a race because you will be at a certain point in your cycle (world records have been set at all phases of the menstrual cycle), it is helpful to keep in mind that hormone levels can have an effect on performance and the next time you have a bad run or workout, think about what factors might be influencing your performance.

Additional studies have looked at the difference between female athletes taking OCPs and those not taking them.  This difference can be tricky to study since a change in hormone levels and core body temperature appears to affect both groups and is dependent on a woman’s individual cycle. However, one study, published in Clinical Physiology asked athletes taking OCPs to exercise for 1 hour in a hot, humid environment at about 60% of their maximum ability. Vital signs such as body temperature and heart rate were recorded.  These same athletes were tested after they stopped taking the pill. Researchers found that OCPs significantly affected core body temperature and heart rate, and this difference was magnified as the duration of the exercise increased. 

Another study examined whether sodium levels and hydration of female endurance athletes was influenced by taking OCPs.  This study asked the athletes to drink a high sodium or low sodium beverage. One half of the athletes were taking OCPs at the time of the study and the other half were not. However, each group was tested during the high hormone phase of menstruation (both natural and controlled by OCPs).  The athletes were then asked to cycle in hot conditions. The athletes who ingested a high sodium drink prior to cycling were able to work out for longer, and their core temperature did not rise as quickly as the low sodium group. This research suggests that during certain parts of the menstrual cycle, for women both on the pill and not, hormones can have an effect on performance and hydration.

However, you should be careful not to drink more liquids or ingest more electrolytes simply because of your cycle. Instead, it is a good idea to monitor your hydration, stay in tune with your body, and be flexible since the amount of liquids and/or electrolytes your body needs may fluctuate along with your cycle.

Another thing to consider regarding hydration, body temperature, heart rate and performance is the chemical makeup of your birth control. Some pills, such as Yasmin, contain drospirenone (drsp), which may increase potassium. Potassium is an electrolyte and it is found in sports drinks such as Gatorade. Proper electrolyte balance is essential for athletes, especially those competing in endurance events longer than a few hours.  If you are considering starting birth control talk to your doctor about how this may influence your hydration, and whether different birth control pills may be better suited for you and your lifestyle.

Still confused? Because of the differences between women and their cycles it is difficult to pinpoint any universal truths regarding exercise, OCPs and the menstrual cycle. Each woman is different and may be affected by these factors in a unique way. It is a good idea to keep track of your cycle and monitor any changes in performance or hydration to get an idea of what works best for you personally. Additionally, the resources listed below may help you to understand how hormones and performance interact.

For more information, check out:
www.knowmycycle.com

J. G Martin, M. J Buono (1997) 
Oral contraceptives elevate core temperature and heart rate during exercise in the heat. 
Clinical Physiology 17 (4), 401–408. 


S.T. Sims, N.J. Rehrer, M.L. Bell, J.D. Cotter (2007) Preexercise sodium loading aids fluid balance and endurance for women exercising in the heat. Journal of Applied Physiology 103: 534-541

C.M Lebrun, D.C. McKenzie, J.C. Prior, J.E. Taunton (1995) Effects of Menstrual Cycle Phase on Athletic Performance. Medicine and Science in Sports and Exercise 27 (3) 437-444

4 comments, add yours | Permalink | Share this article

Tags: birth control pills, body temperature, bone density, drospirenone, drsp, electrolytes, estrogen, heart rate, hormones, hydration and menstruation, luteal phase, menstrual cycle, menstruation, oral contraceptives, oral contraceptives and athletic performance, ovulation, period, potassium, vo2 max, yasmin

Like what you see? Subscribe to our feed!

4 Responses to “The Menstrual Cycle, Oral Contraceptives and Athletic Performance:  How Are They Related?” (Leave a reply)