By Jason R. Karp & Natalie Dau
Adapted from the book Run Like a Woman by Jason R. Karp & Natalie Dau
Although the attention on women’s running seems to be a relatively recent thing, women have been running since the time of ancient Greece. Possibly the first female runner of note was Atalanta, the swift-footed Greek huntress and devoted human follower of the goddess Artemis, who would marry only a suitor who could beat her in a foot race and kill any man who failed to outrun her. It wasn’t until Atalanta was distracted by the apples her suitor Hippomenes rolled onto the racecourse that she lost a race and got married.
Certainly, Atalanta was not aware of her menstrual cycle and its effects on her running back then.
Thousands of years later, we know a lot more about women’s physiology, yet research has found that most female athletes don’t consider their menstrual cycle when planning their training, even though they acknowledge it affects their performance.
The menstrual cycle, which occurs monthly from a woman’s first period (called menarche; age 11 to 14) until menopause (age 45 to 55), is the cycle of hormonal changes from the beginning of one menstrual period to the beginning of the next. It is perhaps the second most important biological rhythm, after our 24-hour circadian rhythms.
When we talk about the menstrual cycle, which is an oddly underdiscussed subject given its essentiality to procreation, what is of greatest interest to runners is the cycle’s fluctuations in estrogen and progesterone, which cause fertilization of an egg and growth of a fetus that will become your son or daughter. Because of the large fluctuations in these two hormones, the phases of the menstrual cycle significantly affect the female runner’s physiology. Variables such as oxygen consumption, body temperature, lung function, hydration, muscle glycogen storage, fat and carbohydrate metabolism, and exercise performance are all affected by the menstrual cycle.
The menstrual cycle is divided into two phases: follicular phase and luteal phase. The first few days of the follicular phase is menstruation (the “period”), when the endometrium (the lining of the uterus) sloughs off, causing you to bleed, which happens because of the rapid drop in estrogen and progesterone when no egg is implanted and you don’t get pregnant. During your period, estrogen and progesterone are at their lowest levels of the menstrual cycle.
The follicular phase begins with menstruation and typically lasts 14 days, but it can last anywhere from 11 to 21 days. Following the period, which typically lasts three to five days, estrogen rises, peaking around day 14, right before ovulation, when it is ten times higher than it was at the beginning of the phase. While estrogen is on the rise throughout the follicular phase, progesterone remains low.
The luteal phase begins with ovulation and is usually 14 days. If no conception occurs within 24 hours of ovulation, estrogen decreases rapidly and rises again to a smaller peak in the middle of the phase (end of week 3/beginning of week 4). While progesterone is low for the entire follicular phase, now it’s progesterone’s time to shine, rising immediately after ovulation. The increase in progesterone, which, at its peak in the middle of the luteal phase, is 25 times the level it was during the follicular phase, causes body temperature to increase to prepare for the fertilization of an egg. If fertilization doesn’t occur, both estrogen and progesterone levels decrease abruptly in the second half of the luteal phase. The rapid drop in progesterone causes water retention, leading to a feeling of being bloated. The phase ends with the start of the period, and the cycle starts all over again.
Although the menstrual cycle is complicated, an easy way to think of it is that the first half—the follicular phase—begins with the period and is dominated by estrogen; the second half—the luteal phase—begins with ovulation and is dominated by progesterone (although estrogen is also elevated in the middle of the luteal phase).
Menstrual cycle-based variations in your running performance may largely be a consequence of changes to your metabolism stimulated by the fluctuations in estrogen. Estrogen alters carbohydrate, fat, and protein metabolism. Females rely more on fat compared to males when exercising at the same absolute and relative intensities. Relying more on fat when running means you rely less on carbohydrates (muscle glycogen and blood glucose), thus delaying glycogen depletion and hypoglycemia (low blood sugar) and postponing fatigue. Progesterone also affects running performance, namely through its influence on body temperature, breathing, and protein breakdown.
In a perfect physiological environment, the menstrual cycle occurs every month and is always the same duration. But that doesn’t always happen, especially among many girls and women who train with high volumes and high intensities and have a low percentage of body fat. Research has shown that female runners experience fewer cycles per year and have greater variability in number of cycles per year, compared to sedentary women.
What happens if your menstrual cycle is irregular or you don’t have a period at all (called amenorrhea)? Perhaps the biggest training-related issue with an irregular menstrual cycle or amenorrhea is the drop in estrogen and the consequential vulnerability to bones. Estrogen, which facilitates the absorption of calcium into bones, is the most important determinant of bone density in women. Any condition that reduces estrogen (e.g., disruption to the menstrual cycle) negatively affects bones. Indeed, estrogen deficiency caused by amenorrhea is the most significant risk factor for osteoporosis in physically active women.
Menstrual Cycle-Based Training
The physiology of the menstrual cycle, with its undulating rhythms of hormones, is all very interesting, even poetic, and understanding it enables you to affect specific outcomes from your athletic endeavors. But what you do with all that information and how you apply it to your training is what matters.
To optimize your training and run like a woman, your plan should be fluid, working with, rather than against or neglecting, your physiology. The rhythm of your training should match the rhythm of your menstrual cycle. Your training must always be open to change, moving workouts around based on the menstrual cycle’s hormonal fluctuations and on how you feel.
Given the variability in individual menstrual cycle experiences among women, training around the menstrual cycle is not an exact science. To simplify the complexity, there are three times during your menstrual cycle when your hormone levels can particularly affect your training, based on their physiological effects:
- Menstruation/early-follicular phase, when both estrogen and progesterone are low (week 1),
- Late-follicular phase, when estrogen is high and progesterone is low (week 2), and
- Mid-luteal phase, when both estrogen and progesterone are high (end of week 3/beginning of week 4).
In general, endurance exercise performance is stronger during the estrogen-dominant follicular phase and weaker during the progesterone-dominant luteal phase. The follicular phase is even associated with better pain tolerance. However, if the secondary peak in estrogen in the middle of the luteal phase is high enough that it counteracts the negative consequences of progesterone, endurance performance can also be strong during the mid-luteal phase.
With this simple, general system—follicular phase stronger and luteal phase weaker—you can optimally plan your training, always remembering to balance how you feel with the science.
Increase your endurance training volume during the follicular phase (especially week 2), when estrogen is high. Refrain from increasing (or slightly reduce) weekly volume during your period and at times of the month when estrogen is low—early- and late-luteal phase (early in week 3 and late in week 4). Avoid challenging workouts during your period, especially if you don’t feel well or if you have menstrual cramps.
The intensity of training can also be planned according to the menstrual cycle. 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 the hard workout, like a long threshold run or intervals, in the second half of the week to avoid your period. If your period is only two to three days, you can do two workouts that week, scheduling them either on Thursday and Saturday, Friday and Sunday, or Thursday and Sunday.
You can also use a block periodization training model, in which you congregate the training stress with two to three hard workouts during the estrogen-high week 2 of the menstrual cycle, and do only one hard workout the week of your period and the other two weeks. This block periodization approach also works well if your period lasts more than four or five days.
The menstrual cycle exerts its greatest training-related influence on aerobic endurance. However, the menstrual cycle doesn’t affect anaerobic capacity and power. Therefore, no specific times of the month are better or worse suited for speedwork (anaerobic capacity and anaerobic power workouts).
When all the pieces of the training program are put together correctly and align with what you need to run faster, the entire training program should function like one fully integrated, beautifully designed system. That system should reflect who you are.
The 25-week 5K/10K training program included here is divided into two phases: general preparation (12 weeks; 3 training cycles of 4 weeks each) and specific preparation (13 weeks; 3 training cycles of 4 weeks each, plus one taper week). The general preparation phase emphasizes aerobic capacity and acidosis (lactate) threshold. The specific preparation phase emphasizes aerobic power (VO2max) and anaerobic capacity.
To make the training program easy to follow, it assumes a four-week (28-day) menstrual cycle, segregated into weeks to correspond to the specific weeks of the menstrual cycle. Week 1 of the training coincides with week 2 of the menstrual cycle, so begin the training program 7 days after the start of your period. Week 1 of the menstrual cycle, which starts with day 1 of your period, functions as a recovery week that completes each training cycle.
As such, the training cycles are planned in the order of weeks 2, 3, 4, and 1 of your menstrual cycle, with 6 days of running planned per week. During estrogen-dominant week 2 of the menstrual cycle (which is the first week of each training cycle), the training load increases in a concentrated block, with several challenging workouts, to take advantage of estrogen’s power. The other three weeks include one hard workout each week. The training program culminates with your target race at the end of week 2 of the menstrual cycle, when estrogen is at its peak.
If your menstrual cycle doesn’t occur in a neat, four-week, 28-day package, or if your cycle duration changes throughout the year, adjust the training week duration, as needed. For example, if your menstrual cycle is 25 days, the follicular phase will be 11-13 days (a training “week” of 5-6 days and a training “week” of 6-7 days) and the luteal phase will be 12-14 days (two training “weeks” of 6-7 days each). If your menstrual cycle is 32 days, the follicular phase will be 18-20 days (two training “weeks” of 9-10 days each) and the luteal phase will be 12-14 days (two training “weeks” of 6-7 days each). (The luteal phase is almost always 14 days, but can range from 12-14 days.)
Before starting the training program, spend time logging your menstrual cycle, with the start of your period as day 1, so you can find your own individual phase duration and pattern.
Each training cycle gives a recommendation for the percentage of peak mileage. Decide what your peak mileage will be for the 100% peak mileage weeks, and then follow the percentage recommendation for each cycle. For example, if you plan to run 80 kilometers per week as your peak weekly mileage, start the training program at 85% of that, which equals 68 kilometers for Training Cycle 1.
Dr. Jason Karp is an award-winning coach, exercise physiologist, author, and founder and CEO of the audio coaching app, KASI (runkasi.com). Natalie Dau is an ultraendurance athlete, social media influencer, and founder and CEO of the lifestyle company, Keeping It Real and the Rockstar Fit App. Their book, Run Like a Woman is available on Amazon.