A few minutes into your high-intensity intervals, you notice your legs feel sluggish. “That’s odd,” you think, since you felt fine just a few days earlier. You shrug it off as just a bad day at the gym and return the next week to do another interval workout. After the first sprint, you can’t believe how good your legs feel. You try another, thinking it may just be a fluke. Again, you feel like you’re flying, like the treadmill belt can’t keep up with you! “How can this be?” you ask yourself. “Just last week I felt so sluggish!” Overhearing your conversation with yourself, a woman on the treadmill next to you whispers as if she was describing a disease, “It’s estrogen.”
Your primary sex hormone, estrogen is the single biggest thing that differentiates you from that guy grunting during bench presses at the gym. It’s a powerful hormone, influencing everything from metabolism to muscle glycogen storage to bone health.
The levels of estrogen and its sister hormone progesterone change continuously throughout your menstrual cycle, which occurs monthly from menarche (age 11-14) until menopause (age 45-50). Although your menstrual cycle is complicated, an easy way to think of it is that the first two weeks (follicular phase) begins with your period and is dominated by estrogen, and the second two weeks (luteal phase) begins with ovulation and is dominated by progesterone, although estrogen is also elevated in the middle of the luteal phase. The luteal phase ends with the start of your period, and the cycle starts all over again.
In general, you can expect to feel better and have better workouts during times of the month when estrogen is the dominant hormone and feel the worst during your period and when progesterone is the dominant hormone. And you may find that, while harder workouts may be more challenging during your period, easy workouts may actually improve your mood and alleviate physical symptoms associated with your period.
However, there’s a lot of variability between women. Some women may have few noticeable effects during their cycle, while others may notice fatigue, difficulty working out in hot weather, cramping, bloating, and increased perception of effort, particularly in the days leading up to and the first few days of their period. Keep a menstrual log to determine how your menstrual cycle affects you and your training.
Perhaps the most significant effect of estrogen is a shift in your metabolism during submaximal aerobic exercise. Specifically, estrogen enhances fat use, which spares glycogen. Because your ability to run is influenced by the amount of glycogen in your muscles, by sparing the amount used and relying more on fat for energy, fatigue is delayed and your endurance is improved. And because your muscles use less carbohydrate during exercise, they also use less protein, since protein only provides significant energy for muscle contraction when muscle glycogen is low.
Since muscular strength and power are proportional to muscle size, you can’t get as strong or as powerful as your boyfriend or hubby since men typically have bigger muscles and more testosterone to make those muscles even bigger. But you can cheat the system a bit if you alter your training based on your hormones and capitalize on being a woman. Although you’re not any stronger at certain times of the month than you are at any other, your menstrual cycle can influence how you respond to your workouts.
The fluctuations in estrogen and progesterone throughout your menstrual cycle alter the ability to build muscle and recover. For example, a study in International Journal of Sports Medicine found that weight training with 3 sets of 12 reps every second day during the follicular phase of the menstrual cycle and once per week during the luteal phase increased maximal quadriceps strength by 32.6 percent compared to just 13.1 percent by training once every third day over the whole menstrual cycle. It seems that doing more training in the estrogen-dominant follicular phase and less training in the progesterone-dominant luteal phase leads to greater strength gains. Estrogen rocks!
Your menstrual cycle also influences your muscles’ sensitivity to storing carbohydrate as fuel. From about day 6 to day 20 of the cycle (mid-follicular to mid-luteal phase), women can take advantage of the body’s increased storage of carbohydrate and consequent favorable conditions for enhanced muscular endurance during both aerobic and high-intensity workouts.
During the early follicular phase and late luteal phase, glycogen stores decrease and endurance wanes. Nutrition becomes of paramount importance in these phases because, with less carbohydrate, there’s greater protein breakdown and suppression of the immune system. Focus on consuming more immune-enhancing ingredients such as probiotics (low-fat kefir and yogurt), antioxidants (green tea, fruits, vegetables, and wheat germ), and vitamin D (wild salmon, tuna, pork loin, eggs, fortified dairy foods, and mushrooms).
Many women who train hard and train a lot and who have a low body fat percentage often experience irregular or even absent menstrual cycles, which reduce estrogen levels. Amenorrhea (0 to 3 periods per year) causes constant low levels of estrogen and progesterone. A woman with amenorrhea has about one third the estrogen concentration and about 10 to 20 percent the progesterone concentration of a normal menstruating woman.
Some women can train a lot and never disrupt or lose their menstrual cycle, while others notice changes in their cycle with relatively little training. High training volumes, low body weight, and endurance sports like distance running increase the incidence of menstrual irregularities. Although a low body fat percentage is desirable to be a better runner, it can negatively impact your menstrual cycle and your health. Research shows that inadequate caloric intake to match caloric expenditure, rather than the stress of exercise, is responsible for the loss of menstrual activity and that consuming more calories to compensate for the large caloric expenditure from exercise can prevent amenorrhea.
Training Around Your Cycle
A female runner’s training program must be strong enough for a man but made for a woman. The principles of training to increase endurance or speed are the same for both sexes. The differences, however, lie in the program’s subtleties. Unlike your boyfriend’s or hubby’s training program, your training program should incorporate more adjustments based on fluctuations of hormones and other female-specific conditions, like amenorrhea and pregnancy. The secret of women’s training is knowing how and when to manipulate your workouts to optimize your training and maximize your results so you can get the largest return on your investment.
Do high-intensity workouts in the lower hormone phases of your cycle, and endurance runs when estrogen is elevated. If you don’t feel well during your period or if you feel bloated from the rapid drop in progesterone as you transition from the luteal phase to the follicular phase, you may want to avoid challenging workouts during those few days. For example, if you have a 28-day cycle starting on Monday, and your period occurs on days 1 to 3 (Monday to Wednesday), plan your hard workout on Thursday or Friday that week.
If you have two hard workouts planned, schedule them on Thursday and Saturday, or schedule just one hard workout the week of your period and two hard workouts during the other three weeks of your cycle. If your period lasts five days (Monday to Friday), schedule one hard workout the week of your period and two hard workouts during the other three weeks of your cycle.
To get the most from your training, understand your cycle and make estrogen work for you. If you train smart enough, not only will you feel better during your next interval workout, you may even be able to challenge the grunting guy on the treadmill next to you.
About the Author
Train right at run-fit.com/trainingprograms.