If you’re a female athlete, you’ve probably had one of those times of the month. No, not that kind (but probably that kind, too). The kind where you felt flat and tired and your workouts sucked, but you didn’t know exactly why.
It turns out, you’re not alone. A growing body of research is developing on women’s cyclical hormonal fluctuations and their effects on exercise and athletic performance. Even the dominant U.S. women’s soccer team started tracking their periods and using the information to make training adjustments. Some of the research shows decreases in coordination and strength and even higher core temperatures during certain periods — but it varies between individuals and there’s still a lot we don’t know.
“There’s no easy answer,” says Xanne Janse de Jonge, PhD, a senior lecturer of exercise at the University of Newcastle, who is now studying the effects of certain birth control pills on forms of resistance training.
In fact, a lack of research on women’s sports performance and the effects of hormones is what led Stacy Sims, PhD, to write a book on the subject, ‘“Roar: How to Match Your Food and Fitness to Your Unique Female Physiology,” which has become a groundbreaker.
“What we actually know is the physiological effects of estrogen and progesterone. What we’re theorizing, based on the science and empirical evidence, is what that means for training around the menstrual cycle,” says Jason Karp, PhD, a coach who co-wrote, “Running for Women.”
Here’s what our experts know about hormones, performance and how to manage the ups and downs. Let’s start at the very beginning.
HOW DIFFERENT PHASES AFFECT PERFORMANCE
FOLLICULAR PHASE
Though menstrual cycles can range from 21–35 days, Day 1 is always the first day of your period. In this first phase, both estrogen and progesterone levels are low. From around days 9–14, estrogen typically increases, with a spike at ovulation. (Estrogen dips slightly after ovulation, but then rises again in the next phase.)
What that means for performance: When estrogen is high (in that second week), you may see an increase in strength or endurance performance. Estrogen typically shifts the metabolism to a greater reliance on fats, too.
LUTEAL PHASE
After ovulation, both estrogen and progesterone levels are high. Both peak about five days or so before your period. If you don’t get pregnant, progesterone levels then fall, your lining is shed and you’re back on Day 1.
What that means for performance: While many women have heavy cramps during their period and can feel terrible, endurance performance isn’t actually necessarily worse. Paula Radcliffe famously broke the marathon world record while having her period.
THE ROLE OF HORMONES
For many athletes, it’s in the days right before their period — as progesterone peaks — that they experience the worst athletic performance. Radcliffe also noted when she attempted to manipulate her period dates with shots or hormone treatments, she actually felt worse — because it was the high hormones, not the bleeding, that caused problems.
Higher progesterone is linked to higher body set-point temperature, which means it takes a higher temperature before your body starts to cool itself. It’s also been linked to increased breathing, which can make workouts feel or seem harder. While VO2 max and lactate threshold actually stay constant throughout the hormonal cycle, if it feels harder then it’s no wonder women sometimes perform slightly worse. There have also been links to reduced reaction times and even coordination.
The caveat is effects vary drastically between individuals. More importantly, there’s still a lot of research left to be done on the topic. Very little work has actually been done directly connecting menstrual cycles and performance, de Jonge says. That’s partially because it’s difficult to control where an entire group of women are in their hormonal cycles to have a scientifically controlled study — and that doesn’t even get into the different kinds of birth control that can affect hormones.
Historically, most sports science research (and, to a degree, medical research) has been done on men. When women were included, it might be just a few in the study cohort and they were often averaged into the overall results instead of noting results might be different for women than for men. So if you’re told you should be feeling X in your training, but instead you’re feeling Y, look into the research behind what you’re being told.
“Ask the question: Was the research on females?” says de Jonge.
HOW TO TWEAK YOUR TRAINING
First, start tracking your period, so you can plan ahead and recognize the symptoms you see at regular intervals.
Second, adjust your training to accommodate hormonal fluctuations. For example, some research has shown you get a better result from strength training five times a week during the first phase and then just once a week during the second phase, because the effects of strength training are greater when estrogen is high. You can plan ahead and know endurance training may feel harder in the second phase and make adjustments to your intervals to account for increased body temperatures and heightened breathing.
The last thing, which is still very much a work-in-progress, is making diet and lifestyle adjustments to accommodate these hormonal changes. This is where Sims’ book focuses. For example, estrogen causes you to burn more fat and utilize carbs less efficiently. So you’ll need more carbs during high-intensity activity, particularly in the premenstrual phase. In general, you also burn more calories during this time. Another thing to consider is, because of the increased temperatures and sodium retention (which results in a bloated feeling), you may want to load up on high-sodium drinks or broths in advance.
WHAT ELSE AFFECTS PERFORMANCE?
Oral contraceptives and menopause can both have a big impact on hormone levels, says Karp. After menopause, estrogen decreases significantly. For women on oral contraceptives, the effects vary depending on the pill and how it works, because each pill delivers a set amount of estrogen and progesterone. There is research suggesting oral contraceptives can have a negative impact on performance, because they essentially put a woman into an artificially high hormonal state throughout the month.
However, de Jonge also notes that much of this work was done on older models of birth control, while modern pills tend to have lower, more targeted doses. She pointed to other research that showed women not on oral contraceptives had a greater increase in performance from high-intensity interval training, but the women on oral contraceptives lost less of their fitness four weeks later. Another highly touted study found a potential link between fewer ACL tears and birth control. Women typically have a higher rate of ACL tears than men. This is thought to be because of over-flexibility and tendon issues during hormonal fluctuations. It is hypothesized that the consistent hormonal levels of contraceptives eliminated some of those issues and increased muscle stiffness.
THE BOTTOM LINE
With so much still left to be studied and so many individual variables, the best place to start is conducting your own personal study. All our experts recommend beginning by tracking your period, hormones, symptoms, activity levels and performance. See if you spot patterns. Then you can put some of these tips into practice and test different hypotheses. Maybe by understanding your hormones and working with them — adjusting your diet or your strength training — you’ll find a whole new level of performance.
