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A few minutes into your high-intensity intervals, your legs feel sluggish. You shrug it off as just a bad day at the gym. Then the very next week you’re flying high for your interval workout and feel like the treadmill belt just can’t keep up with you. How could this be? Your eating habits were the same both weeks, you got the same amount of sleep and you didn’t change your lifestyle in any way. The answer could lie with estrogen.
Estrogen is a woman’s primary sex hormone, and it’s the single biggest thing that distinguishes you from that grunting guy on the bench press next to you. It influences everything from metabolism to glycogen storage to bone health, and its presence or absence could be the key to having a great workout.
How to Make Estrogen Your Training Partner
You can actually make your hormones work for you instead of against you.
Your hormonal environment is constantly changing, and the levels of estrogen and its sister hormone, progesterone, fluctuate continuously throughout your menstrual cycle. During the first two weeks — the follicular phase — of your cycle, your body’s hormones are dominated by estrogen; the second two weeks — the luteal phase — begins with ovulation and progesterone takes over as the primary hormone. At the end of that phase, you start your period and restart the cycle.
So what does all this mean for your workouts? In general, you can expect to feel and perform better for demanding workouts when estrogen is high and feel the worst during your period and when progesterone is at its peak during the late luteal phase and into the early follicular phase.
“While some women may have few noticeable effects during their cycle, others may notice fatigue, difficulty working out, cramping, bloating and increased perception of effort, particularly in the days leading up to and the first few days of their period,” says Dr. Carolyn Smith, executive director of Marquette University’s Medical Clinic, medical director for Marquette’s Department of Intercollegiate Athletics and co-author of Running for Women (Human Kinetics, 2012).
But there’s more to the equation than just avoiding hard workouts during the low-estrogen phases. Here’s how to optimize different types of training throughout your menstrual cycle.
Best Times for Strength Training
Focus your hardest strength-training workouts when your estrogen is at its highest during the follicular phase: days six to 14.
A study in the Inter-national Journal of Sports Medicine found that doing more weight training in the estrogen-dominant follicular phase and less training in the progesterone-dominant luteal phase led to greater strength gains in the quadriceps.
“The fluctuations in estrogen and progesterone throughout your menstrual cycle alter the ability to build muscle and recover,” says Stacy Sims, Ph.D., exercise physiologist and co-founder of Osmo Nutrition (osmonutrition.com). Take advantage of those peak estrogen-dominant days in the first half of your cycle to work on your muscle tone.
This doesn’t mean you have to stay away from the gym during the progesterone-dominant second half of your cycle — just make sure to increase your protein consumption before and after training during this time. Progesterone is catabolic, which reduces the body’s ability to recover and build muscle.
Best Times for Cardio
Plan your longest cardio workouts for the middle of your cycle: days six to 20.
Elevated estrogen levels cause a shift in your metabolism during aerobic exercise, allowing you to burn more fat.
“Estrogen enhances fat use, which spares glycogen,” Smith says. “By sparing the glycogen used and relying more on fat for energy, fatigue is delayed and your endurance is improved.” During this phase, your body’s enhanced glycogen storage will also spare unwanted muscle breakdown during cardio because your body taps protein for energy when glycogen is depleted.
“From day six to 20, women can take advantage of favorable glycogen-storage conditions for enhanced muscular endurance,” says Kim Mueller, MS, RD, CSSD, owner of Fuel Factor and co-author of The Athlete’s Guide to Sports Supplements (Human Kinetics, 2013). “In contrast, during the early follicular phase and late luteal phase, glycogen stores drop off and endurance wanes.”
When to Avoid Hard Workouts
You may want to delay tough sessions at the gym during your period: days one to five (depending on how long your period lasts).
If you feel bloated from the rapid drop in progesterone as you transition from the luteal phase to the follicular phase, consider avoiding high-intensity or long-endurance workouts during those few days.
For example, if you usually do two hard workouts per week and have a 28-day cycle starting on Monday and your period occurs on days one to five (Monday to Friday), schedule just one hard workout on Sunday for the week of your period and two hard workouts during the other three weeks of your cycle.
If you want to get the most from your training, understand your cycle and make estrogen work for you. And if you train smart enough, not only will you feel better during your next workout, but you also may even be able to challenge that grunting guy bench-pressing next to you.