Is it safe for women to run marathons? This question lingers in the back of my mind whenever I start looking for a new race or making a training plan. If you, like me, are a runner who thrives on the adrenaline of race day and hopes to one day qualify for the Boston Marathon, maybe you too have found yourself asking this and related questions. Is the stress I’m putting on my body through marathon training going to negatively impact my cycle or fertility? Could long-distance races harm my overall health? Are my three-hour training runs actually the stress relief I describe them as, or are they wreaking havoc on my hormones?
Different doctors will likely give you different answers, and of course, every woman is different. Some of us can tolerate more stress than others, and the way that endurance training impacts our unique cycles and hormone levels is going to vary. So is it safe for women to run marathons? The short answer is, “it depends.” Although there is no one-size-fits-all answer, there are some things you should be aware of before you decide to take on 26.2 miles.
Endurance training and cortisol levels
We’re all familiar with cortisol, aka “the stress hormone.” But did you know that endurance training (running included) actually increases cortisol levels in your body? It’s true.
When the body is under stress, the hypothalamus signals the adrenal glands to produce cortisol. This anti-inflammatory hormone is helpful at moderate levels. By increasing blood sugar and suppressing the digestive and reproductive systems, cortisol can be quite effective at helping you outrun a lion (or get to the finish line first!). That being said, it is important to be mindful of the long-term effects of heightened cortisol exposure.
A 2012 study of endurance athletes examined the relationship between exercise and stress [1]. Using hair segment analysis [2], the researchers were able to retrospectively measure cumulative cortisol levels in the athletes’ bodies over prolonged periods of time. The results indicated that the intensity of endurance training is positively correlated with levels of cortisol in the body. In other words, the athletes who trained more intensely had higher cumulative levels of cortisol, even if they maintained a low-stress work and home environment.
Female runners and pregnenolone steal
For female runners specifically, it is important to be mindful of how training (and increased cortisol) will impact hormone levels, and therefore menstrual cycles. If a woman’s body experiences high levels of stress for a long period of time, one theory posits that it may revert to “pregnenolone steal,” which is a secondary means of producing cortisol.
For female runners specifically, it is important to be mindful of how training (and increased cortisol) will impact hormone levels, and therefore menstrual cycles. If a woman’s body experiences high levels of stress for a long period of time, one theory posits that it may revert to “pregnenolone steal,” which is a secondary means of producing cortisol.
According to this theory, pregnenolone steal occurs when the body prioritizes the production of stress hormones over hormones deemed less necessary, such as those for reproduction. Bypassing the typical means of cortisol synthesis, the body will begin to make cortisol out of pregnenolone, the precursor to the hormone progesterone (and other sex hormones, too). This could impact the luteal phase of the menstrual cycle, which is maintained by progesterone. This could subsequently lead to anxiety, poor mental health, worsened premenstrual syndrome (PMS), and even amenorrhea.
However, some integrated health professionals believe that the process is far more complex than this theory suggests. For starters, the pregnenolone steal theory seems to assume that pregnenolone is “stolen” from “one giant pool” to make cortisol when the body is under acute stress. In fact, pregnenolone is synthesized (produced) inside the cells of various organs (not one giant pool) in the body. Far from being a simple function of too much stress=too little pregnenolone, “the conversion of pregnenolone into other hormones [including cortisol] is determined by the type of endocrine gland itself, as well as enzymes, cellular signals, regulatory hormones and gene activity.”
If pregnenolone steal doesn’t explain menstrual cycle issues in female athletes, what does?
In all reality, when your body experiences high levels of stress, your brain will “downregulate reproduction by reducing [the] production of FSH [follicle stimulating hormone] and LH [luteinizing hormone].” Both of these levels must be high enough in order for ovulation to occur (and remember, without ovulation, the release of a mature egg from an ovary, there can be no conception). In other words, if you’re worn out from being chased by a lion, your body will simply stop producing FSH and LH at levels high enough to conceive.
How to promote hormone health as a runner
With all of this in mind, female runners who decide to tackle long distances can seek to optimize their health by mitigating the effects of cortisol and prioritizing holistic wellness. To do this well, they need to prioritize the following:
Rest, rest, rest
Although the temptation to train every day might be strong, runners should not underestimate the importance of rest. Getting good sleep (think 7-9 hours nightly) is important for not only physical recovery, but also for hormone production. Truly letting your rest days be restful will give your body time to recover and prepare for the next week of training.
Strength train
Many marathon training plans include 3 days a week of strength training, and for good reason! Strength training is important for all athletes, but especially for women. It not only increases bone density, decreases muscle imbalances, and reduces injury risk, but improves the cortisol:testosterone ratio in your body. Maintaining healthy levels of testosterone will improve muscle growth and manage the impact of cortisol on the body.
Prioritize nutrient-dense foods
Endurance athletes need to eat a balanced diet in order to recover from long runs and support their hormone health. Preparing meals that are high in protein, carbohydrates, and healthy fats is a great way to optimize nutrition. Additionally, making sure to consume enough iron is important for female athletes. Anemia, or iron deficiency in the blood, is linked with the female athlete triad and can cause fatigue. Good sources of iron include red meat, spinach, seafood, molasses, nuts, and legumes.
Chart your cycle
Last, but potentially most important, female athletes should chart their cycles. The menstrual cycle is a fifth vital sign for women, so any woman seeking to optimize her health or athletic performance will only gain helpful insight by embracing this practice. Being aware of your typical cycle patterns, and any changes that occur while training, will allow you to adjust your training plan or diet to better meet your body’s needs.
Being aware of your typical cycle patterns, and any changes that occur while training, will allow you to adjust your training plan or diet to better meet your body’s needs.
It is not uncommon for female athletes to observe changes in their cycle charts as they increase their mileage, but it is never normal to lose your period altogether. Additionally, it is important to observe a return to cycle normalcy in the months following the race.
Cycle chart signs indicating you might need to slow down
If you lose your period for 3 or more months during training, also known as exercise-induced amenorrhea, your training may be disrupting your hormones or causing other issues. If you notice changes in your cycle, especially the absence of your period, a shortened luteal phase, or mid-cycle spotting, be sure to contact your doctor. You might also consider decreasing your weekly mileage and adding a healthy snack at the end of the day. Great options include avocado toast with olive oil, a peanut butter banana smoothie, or greek yogurt with berries and nuts!
Performance can fluctuate with the phases of your cycle… be gentle with yourself!
If you’re a runner who charts her cycles, cycle syncing your workouts can be a great way to improve your performance. As your hormone levels fluctuate, so will your athletic abilities (and your risk for injury). Taking steps to work with your body rather than against it will boost your performance in the long run (no pun intended)!
For example, during the follicular phase, you may notice higher energy levels and increased pain tolerance. Additionally, your insulin sensitivity will be higher, meaning this phase is conducive to high intensity training and speed workouts.
Around ovulation, you will likely have higher energy levels, but you may also be more susceptible to certain types of injuries. Because of the way estrogen impacts collagen structure, you are 4-8x more likely to experience an ACL tear, among other injuries, around ovulation. Focusing on weight training is a good way to take advantage of high energy without risking injury.
Finally, during the luteal phase, you may notice that high-intensity training and speed workouts are more difficult. This is because progesterone may decrease insulin sensitivity, keeping your blood sugar high in order to transport as many nutrients as possible to the endometrium [3]. This means your muscles will not store as much glucose, which can cause lower energy levels during workouts. Because of this, the luteal phase is a great time to go for easy, long runs or base runs, all with a focus on fueling well. Make sure to eat plenty of protein, as higher levels of progesterone can also increase the breakdown of protein and muscle in the body.
The bottom line on whether marathon training is safe for women
So, back to the original question: is it safe for women to run marathons? Although there is no clear-cut, simple answer, if you are healthy and focus on maintaining hormone health with good nutrition, balanced workouts, and recovery, then running a marathon is certainly an awesome goal. Just make sure to be mindful of your unique needs as a female athlete and take steps to manage the stress of training so you can keep chasing your athletic goals long into the future!
I remember asking an OBGYN if it was safe to run a marathon pregnant. He said no, but since he was wildly obese and clearly didn’t have a handle on his own health, I ignored him and ran it anyway at 10 weeks pregnant. It was a wonderful experience. Then it became my tradition (running a marathon or half-marathon during every pregnancy). Yes, running marathons are ABSOLUTELY okay for women to do safely, even while pregnant — just use your brain and listen to your body.
Something to think about for tweens and teens. I was a cross country runner during my adolescence and had a really competitive male coach that made young women train as hard as the young men. Looking back, I think training so intensely was unhealthy for my body during a very important time – the time of puberty. It may have contributed to underdeveloped body parts (like breasts), to delaying my menstrual cycle until I was sixteen, and to making me more vulnerability to issues with anxiety. While I cannot rule out genetics in these issues, I can say that there is a strong correlation between the physical and mental hardships I faced and still face, and the intense training and strain being placed on my body. Parents, please be mindful of children during puberty to help optimize their health and not stunt their growth and development.