In recent years, more and more coaches and athletes have been turning their attention to the female menstrual cycle, specifically considering how it affects training and athletic performance. Are we limited to reacting to the symptoms of our cycles, or are there strategies for adapting our training to work WITH our cycles instead of trying to push through a planned training session that may not be ideal for the state of our bodies at the time.
I’ve done a fair bit of research and have found a limited amount of recent scientific (white paper) research. I’ve also listened to podcasts and webinars, read Stacy Sims’ book, ROAR, and read many other articles and papers on this topic. I’ve tried to condense what I’ve learned into the most simple and digestible format possible, and while there is some conflicting information, I want to put it all out there and allow each of you to determine how you want to use it. Some information may ring true for you and others may not. This is a big topic and has many branches, so I apologize for the length of the post, but want to touch on each piece briefly.
The one real key takeaway is that each woman, athlete or coach should use her own history and experience to modify and plan training, as no two women will experience the same symptoms or effects of our monthly hormonal fluctuations. When it comes to knowledge, some can be powerful, but too much can be a hindrance. I think this is good info to know and keep in mind, but shouldn’t necessarily dictate how you set up your training schedule or plan your race season. I think there’s still value in experimenting to find what works for our individual bodies, and listening to and understanding what’s going on and using that info to adapt and move forward accordingly, rather than restricting ourselves to what we “should” do at certain times and never deviate from the recommendations. You may be surprised at what you’re capable of when you’re not “supposed to” be.
Part 1- The menstrual cycle, in review. What exactly is happening and how does it affect exercise/training/performance?
The average woman’s menstrual cycle takes 28 days to complete. Some individual variation is normal and can actually range from 24-35 days. The primary purpose of the menstrual cycle is to prepare for reproduction. The fluctuation of the primary sex hormones estrogen and progesterone are a result of the body preparing for ovulation, implantation and egg fertilization. If fertilization does not occur, a new cycle begins. So let’s look at the specifics of the cycle:
Days 1-14: Follicular Phase- estrogen low, progesterone low (Days 1-7: Menstrual phase)
- As a result of an unfertilized egg, the lining of the endometrium and the unfertilized egg are shed, resulting in menses, or the period.
- The pituitary gland stimulates the release of Follicle Stimulating Hormone (FSH), which signals the ovaries to prepare an egg. Estrogen levels rise throughout the follicular phase, which stimulates the mature egg to release and begin the ovulatory phase, usually between days 14-16.
- Typically, the amount of blood lost in a period is not enough to impact exercise performance.
- When the period is finished, estrogen levels begin to rise, reconstructing the lining of the uterus.
Effects on Exercise:
Endurance may be reduced so you’ll benefit from shorter workouts during this phase.
Some research indicates increases in pain tolerance, endurance and insulin sensitivity during this phase (1).
Many studies show that muscular strength and anaerobic performance do not seem to be affected, while other studies show conflicting results.
Evidence for strength training during the follicular phase:
- 3 groups performed a 4 month resistance training program: Group 1 performed lower body resistance training 5 days/week for the first 2 weeks of each menstrual cycle. Group 2 performed the same high frequency leg training for the last 2 weeks of the menstrual cycle and the control group performed leg resistance training 3 days/week throughout.
- Participants in group 1 increased lean body mass of the legs, improved their jump height, and peak hamstring torque, as well as recorded positive experiences of the training. Group 3 demonstrated increased jump height and hamstring torque, and group 2 showed no significant results.
- It is also worth noting that none of the participants reported negative consequences of the training protocol, and there were no clear differences between women with or without oral contraceptive use (4).
Days 14-16: Ovulatory phase- estrogen high, progesterone low
- Peak estrogen levels trigger luteinizing hormone, which releases the egg that had been maturing during the follicular phase
- Ovulation only lasts 3-4 days
- Slight rise in body temperature around day 14 when ovulation begins
- The immune system is less efficient at warding off infections due to the rise in estrogen.
Effects on Exercise
- May increase hydration needs as body temperature is increased, but it shouldn’t be a significant change.
- Estrogen is anabolic, so this is a great time for strength training (low volume, high intensity). Just make sure to warm up well, including muscle activation and joint stability exercises to help prevent injury and prepare for high intensity exercise.
Days 15-28: Luteal phase- estrogen moderate, progesterone high
- Estrogen remains high from the ovulatory phase and continues to rise in the luteal phase
- PMS symptoms are experienced in this phase: bloating, headaches, food cravings, trouble sleeping, etc.
- Progesterone rises and prepares the endometrium for implantation
Effects on Exercise
- Absolute and relative VO2 max were slightly reduced in one study during the luteal phase as compared to the follicular phase. This could have significant impacts on some women, but it was not statistically significant in the given research study (2).
- Another study (on sedentary women, no research found on athletes specifically) showed increased resting and decreased peak heart rates during both the luteal and menstrual phases. Higher heart rates during this phase are more problematic in hot and humid environments.
- VO2 max and endurance were reduced in the follicular and menstrual phases.
- Running economy was impaired at exercise intensities that were applicable to training and performance in the mid-luteal phase, when core temperature and minute ventilation are increased. In physiologically stressful environments, this impairment in running economy may have a significant impact on training and performance (3).
- Some studies show that hemoglobin, ferritin and percent transferrin saturation decrease in the luteal phase (5) while others report little impact on the most important biomarkers: hemoglobin and hematocrit (6).
Implications for training/racing:
- If you’re doing high intensity cardio sessions during the luteal or menstrual phases, expect them to be a little harder; your heart rate will likely be higher overall, but you’ll also have trouble reaching your “normal” peak heart rate.
- It is recommended to use something objective (not heart rate) to measure your intensity during training, such as power, speed, or pace.
- Strength workouts are rarely compromised by your cycle, so if you’re not feeling up to a cardio session, hit the weights instead of doing nothing.
- Often a light workout can help you feel a little better when you’re feeling lousy from PMS symptoms.
- During the luteal phase, the peaking of estrogen and progesterone can cause an increase in fluid retention, which redistributes throughout the body, causing a decrease in plasma volume, resulting in a decrease in the amount of oxygen that can be delivered to the working muscles, reducing sweat rate and increasing heart rate.
- This has also been linked to a decreased time to exhaustion as a result of an increase in body temperature so you’ll need to pay attention to your hydration needs in this phase.
Implications for training/racing:
- These factors make hydration especially important during this phase, especially in hot and humid environments. Since we can’t schedule races and events around our menstrual cycles, pre-loading with specially designed formulas high in electrolytes may be worth considering.
What else is important to know?
Iron: Women typically lose 16mg of iron during a normal period, more if you have heavier menstruation- that’s 0.4-0.5% of total body iron.
- This shouldn’t have much of an mpact, however, if you’re craving a steak or burger, you may need to top up your iron.
- Recommended dietary iron intake during your period is 18mg per day
- Animal based iron (heme) such as lean red meat, sardines, mussels and oysters is more easily absorbed by the body than vegetarian sources (non-heme) such as beans, dark leafy greens and fortified whole grains.
- You can maximize absorption by pairing iron rich foods with foods high in vitamin C, such as citrus fruits.
CRP (C-Reactive Protein, a marker of inflammation) levels fluctuate based on training stress, nutrition, lifestyle stress, and your cycle.
- Studies have shown that CRP levels tend to be at their highest during menstruation, then steadily decrease until the expected day of ovulation, then increase throughout the luteal phase. High CRP levels have been positively associated with PMS symptoms (9).
Implications for training/performance:
- Adding exercise-induced inflammation (as a result of hard training) on top of higher baseline levels of inflammation (as a result of hormonal changes) will result in longer recovery times after hard training during the luteal phase and early in the menstrual phase.
- Focusing on anti-inflammatory foods and utilizing recovery modalities such as compression and massage can help improve recovery dur ing these phases.
It’s important to get as many nutrients as possible through whole foods, rather than supplements, however some supplementation can be beneficial.
- Vitamin D
- Vitamin D levels have been shown to fluctuate during the menstrual cycle. Levels are highest during your period and lowest during the luteal phase when PMS symptoms begin.
- Vitamin D supplementation during the luteal phase provides PMS symptom relief for many women (8).
- The upper limit for safe Vitamin D supplementation is 4,000IU/day.
- Vitamin D is stored in body fat, so people with higher body fat percentages will have less of the vitamin in their circulating blood.
- Inflammation can also reduce circulating levels of vitamin D in the bloodstream (related to CRP below).
- Women are naturally better at burning fat for fuel compared to men, especially during the follicular phase.
- During the luteal phase, however, when fueled by carbohydrates, there was no detriment to performance. This is because estrogen and progesterone peak during the luteal phase and suppress gluconeogenesis (the body’s process of generating glucose out of non-carbohydrate sources when glucose or glycogen are not readily available). This makes performance in a fasted state extremely difficult and makes carbohydrate fueling critical during endurance events (10).
- The breakdown of protein and muscle peaks in the luteal phase, increasing protein needs during this time, especially during high intensity training and if you are a woman in perimenopause or menopause (10).
Hormonal birth control and oral contraceptives (including past use) can be responsible for increased levels of SHBG (sex hormone binding globulin) and decreased levels of DHEAS and testosterone.
- SHBG is a protein that is responsible for transporting testosterone and estrogen throughout the body. It regulates the amount of free or circulating hormones that are available to your body for use. Without adequate levels of active sex hormones, your energy levels, sex drive, memory and recovery from training will be negatively affected.
- Hormonal contraceptives can result in a 400% increase in SHBG levels. This affects adaptation and recovery from training because more testosterone will be bound to SHBG, leaving less available to the body for use. OC’s with lower doses of estrogen, like IUD’s will affect SHBG less than those with higher doses, such as the patch or ring.
- DHEAS is used to make the sex hormones estradiol and testosterone. DHEAS levels naturally peak around age 30 then steadily decline.
- Healthy DHEAS levels indicate a healthy immune system, increased energy, strong bones and muscles, good sexual function, and lower risk of developing heart problems with age.
- Low levels of DHEAS may be a result of over-exercising, low energy intake (especially fats), high stress levels and oral contraceptives. DHEAS levels drop quickly once beginning the use of birth control due to the suppression of androgens and high cortisol levels. DHEAS levels can take a significant amount of time to restore upon the cessation of birth control.
- Testosterone is produced in the ovaries and is responsible for muscle building, protein synthesis, and increasing bone density. Testosterone levels naturally decline with age and remain very low at the onset of menopause.
- Oral contraceptives can inhibit testosterone production by 50% (11).
- One negative impact of this is an inhibited ability to recover, build muscle and positively adapt to a training stimulus.
- Cortisol levels can also be elevated. The adrenal glands suppress the production of androgens (see the point on testosterone above…not a good thing for athletes), thereby stimulating more cortisol production in order to siphon off the products that would otherwise go towards making androgens, like testosterone.
- Low grade inflammation has been linked to OC’s so you will likely have increased hsCRP levels.
- Folate levels will decrease. This is a vital nutrient during the early stages of pregnancy, so if you’re taking birth control but may want to have children down the road, you’ll want to supplement with folate in preparation and probably have your folate levels checked before trying to get pregnant.
- Women taking oral contraceptives are advised to make lifestyle modifications such as combating inflammation with antioxidants like vitamins A, C & E, increasing sleep, reducing stress and ensuring adequate calorie and fat intake.
*The contraceptive methods with the least amount of negative effects are IUD’s and progesterone-only oral contraceptives.
- The fluctuations of hormones seem to have a greater impact on endurance performance as compared to strength training. Aside from any negative effects of PMS during your cycle, the hormonal changes show no significant impact on muscle fatigue or strength (6).
- General guidelines cannot be made regarding exercise performance around the menstrual cycle, however, that’s not to say that women should not make individual modifications to their training and exercise routines based on their personal responses to the menstrual cycle (12).
One article suggested that endurance athletes modify their competition schedule around their cycles, especially avoiding events in hot and humid conditions during the luteal phase. This is primarily due to the challenges brought on by an increased body temperature and changes in metabolism, which make performing, training and recovery especially difficult during the luteal phase. In theory, this is great, however, I don’t think this is a realistic recommendation. Endurance athletes don’t get to choose when major events like National and World Championships are held, and skipping an event of that significance because we’re not at the ideal time of our cycles is not an option. So what happens when we skip events that fall during the luteal or early menstrual phases in order to optimize performance, and then World Championships fall during one of those phases? We’d be completely unprepared and at a huge disadvantage, both physically and psychologically.
In my opinion, I think it’s advisable to track our cycles and patterns and learn our bodies as best we possibly can. This can help us learn how we each respond individually, and how we may need to adapt our training sessions or cycles accordingly. I think we should race at all times during our cycles so we can better understand and practice the modifications we need to make in order to adapt and overcome these challenges to the best of our abilities and be better prepared for a competition that lands during one of these times. And while we can’t do anything about the “disadvantage” of our cycles not lining up with big events at the right times, we can still do our due diligence in preparing as best we can.
There is a lot more related information on this topic that I’ll continue to share, so keep an eye out for future posts about tracking our cycles and what we can learn from that information, nutrition considerations for women, training adaptations as we age, and more.
Other helpful resources:
Nourish, Balance Thrive Podcast interviews Mikki Williden, PhD. “Women Athletes: Nutrition, Supplementation, and Hormones”
WILD AI- an app to help track your cycle, symptoms and provides recommendations based on your cycle phase
InsideTracker.com has some great articles on this topic, though there is a lot of overlap with this article. Here's How Birth Control Can Affect Your Biomarkers
Fischetto, G, & Sax, A. The menstrual cycle and sport performance. New Studies in Athletics, 28(3/4): 57-69. 2013
Goldsmith E, Glaister M. The Effect of the Menstrual Cycle on Running Economy. J Sports Med Phys Fitness. 2020 Apr;60(4):610-617. doi: 10.23736/S0022-4707.20.10229-9. Epub 2020 Feb 4.
Training and Hormones in physically active women: with and without oral contraceptive use.
Doctoral Thesis, comprehensive summary (2016) Umea University, Faculty of Medicine, Department of Community MEdicine and Rehabilitation, sports medicine
Belza A, Henriksen M, Ersbøll AK, Thilsted SH, Tetens I. 2005. Day‐to‐day variation in iron‐status measures in young iron‐deplete women. Br J Nutr 94:551–556
Janse de Jonge X. Effects of the Menstrual Cycle on Exercise Performance. Sports Medicine. 2003;33(11):833-851. doi:10.2165/00007256-200333110-00004)
Sims ST, Rehrer NJ, Bell ML, Cotter JD. “Pre-exercise sodium loading aids fluid balance and endurance for women exercising in the heat.” Journal of Applied Physiology, 103: 534–541, 2007
Arman Arab, Sahar Golpour-Hamedani, Nahid Rafie. 2019. The Association Between Vitamin D and Premenstrual Syndrome: A Systematic Review and Meta-Analysis of Current Literature. J Am Coll Nutr. Sep-Oct 2019;38(7):648-656. doi: 10.1080/07315724.2019.1566036. Epub 2019 May 10.
Sims, S., Yeager, S. 2016 ROAR. Rodale Inc. NY
Zimmerman, Y., et al. “The effect of combined oral contraception on testosterone levels in healthy women: a systematic review and meta-analysis.” Human reproduction update20.1 (2014): 76-105.
McNulty, K.L., Elliott-Sale, K.J., Dolan, E. et al. The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis. Sports Med 50, 1813–1827 (2020).