How Your Menstrual Cycle Affects Performance

With all the changes in hormone levels that occur during your menstrual cycle, you'd expect speed workouts to suffer during your period, right? Wrong. Surprisingly, near the end of your period, your body is actually geared to pegging track workouts and tempo runs. However, your long, slow runs will suffer. Read on to learn how your training and racing is affected by your menstrual cycle.

The fluctuation of your energy levels

Your menstrual cycle is composed of three phases. The first phase, generally days one through thirteen (the first three to seven days being menstruation), is called the follicular phase and is marked by relatively low levels of estrogen, except for a spike near day fourteen. The next phase, called ovulation begins on day fourteen. The remainder of the cycle, days fifteen through 28 of the average 28-day cycle, is called the luteal phase and is characterized by moderately high and stable levels of estrogen. Estrogen levels are important because estrogen is the key hormone affecting not only your cycle, but also the type of fuel available for your working muscles. Studies have shown that low levels (in the follicular phase) favor the breakdown of quick energy stores (muscle glycogen) whereas high levels (in the luteal phase) favor fat-burning, lower lactic acid levels and glycogen sparing.

How does this relate to training?

Say you've planned your track workouts for every Wednesday. You go to the track during your follicular phase (low estrogen) and hit all your repeats right on. You leave the track with confidence and excitement. A few weeks later, you go to the track but you're now in the luteal phase (high estrogen). You feel sluggish, tired and lethargic. You feel like you have a totally different body. You leave the track doubting your abilities and your training program, despite the fact that your long runs have been successful. Don't feel discouraged, though. It's not for lack of training that you're performing this way, it's the way your body is fueling your workouts. In the follicular phase you benefit from a quick breakdown of carbohydrates for speed and efficiency. Your body is primed for providing quick energy for fast running In the luteal phase, however, your body is in the fat-breakdown mode – fueling your workout primarily through increased utilization of fat. Since fat is a source of slower, more sustained energy than carbohydrates, your intensity may suffer during the luteal phase. Basically you're trying to run high-octane workouts on low-octane fuel. In other words, during the luteal phase your long, slow runs will feel easier and require less recovery time because your body will take advantage of increased fat breakdown. In the follicular phase your tempo runs and interval training will feel easier because you'll be accessing quick energy through carbohydrates. Of course, this doesn't mean you shouldn't do long-distance workouts in the follicular phase or tempo workouts in the luteal phase. Just keep in mind that faster running may feel harder in the luteal phase, while slower running may feel more difficult in the follicular phase. With this new understanding of your menstrual cycle and the fueling mechanisms that change from phase to phase, don't view your cycle as a training disadvantage but rather a training secret. Use what nature gave you as your ergogenic aid and have confidence in your training. Sorry, men, but maybe estrogen is the wonder hormone after all!

References

Brooks, Exercise physiology (2nd ed.), Mayfield, 1996
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Scandinavian Journal of Medical Science & Sports, Vol.1, 1991
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The Physician & Sports Medicine, Vol.14, 1986
Clinics in Sports Medicine, Vol.13, 1994
European Journal of Applied Physiology, Vol. 69, 1994

Credits

Run The Planet thanks Peak Running Performance for the permission to reprint the article "The Menstrual Cycle and Your Performance" by Stacy Sims, M.S. Copyright © 1999 Peak Running Performance. All rights reserved. Illustration © 2005 by Run The Planet.