• New research involving almost 4,000 elite athletes found that muscle and tendon injuries were most likely around the time the athletes were ovulating.

• The study also found that injuries were more likely when the athletes’ periods were late.

• Tracking your training in relation to your period could provide valuable insight on avoiding injury.

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While a lot of runners track their periods so they can be prepared with the appropriate supplies, many don’t realize that monitoring their cycle may also help them gain insight into their potential risk of injury.

A recent study in Frontiers in Physiology following elite English soccer players found the athletes were almost twice as likely to sustain muscle and tendon injuries mid-cycle, near ovulation, compared to at other times. Whereas other research has similarly shown mid-cycle to be a riskier time for getting hurt, those studies focused solely on ACL injuries. The only other paper to look closely at all types of injuries found athletes to be at a higher risk of getting hurt while getting their periods, a notion that’s commonly cited, but has some methodological faults. That study didn’t clearly define the cycle’s phases or differentiate between different types of injury.

The new study is part of a growing body of research that has found the opposite: There’s a greater risk of athletic injury near ovulation, when an egg is released from the ovaries, compared to other times in the cycle.

A typical menstrual cycle for those not using hormonal birth control lasts 21 to 34 days and is counted from day one of getting your period until day one of the next period. It’s divided into stages by ovulation—the follicular phase before ovulation and the luteal phase after.

The new study tracked the menstrual cycle phases even more closely, differentiating between the follicular and late follicular phases. During the late follicular phase, defined as the three-day period preceding and including ovulation, estrogen peaks, and can be about 10 times higher than in the early follicular phase. Although there’s some debate as to how exactly estrogen impacts the body’s tissues, it appears that fluctuations of the hormone may play a role in injury risk, possibly by affecting tendon and ligament stiffness.

It was during the relatively short time surrounding ovulation that the nearly 4,000 soccer players were most likely to sustain injuries including muscle ruptures, tears, strains, and cramps, as well as tendon injuries and ruptures.

This tracks with what Ashley J. Bassett, M.D., an orthopaedic sports medicine surgeon, sees in practice. She notes that, while many of her young, active female patients are on oral contraceptives, among those who aren’t, she has observed an increased incidence of injuries mid-cycle compared to at other times.

As you begin to compare your cycle with your runs, you may notice themes that emerge over time that can influence the way you structure your training.

Additional Challenges

Additionally, the study found athletes may be more prone to injury, especially joint and ligament injuries, when their period is late, a possible indicator of Relative Energy Deficiency in Sport. RED-S is a condition in which athletes don’t take in enough calories to meet their energy needs, and it can have detrimental effects on the body’s systems, including hormonal changes and loss of regular menstruation. This can lead to loss of bone density as well as a host of other health problems.

RED-S, which was formerly known as the female athlete triad, is often missed or misdiagnosed. Treatment is often multidisciplinary, and can involve strategies for increasing nutrition, decreasing training, and addressing any psychological components.

For this reason, Catherine Logan, M.D., an orthopaedic sports medicine and shoulder surgeon, says, “We should be screening all female athletes for this condition, as it can occur across all types of sports and levels of play.”

Runners, elite athletes such as those in the study, and others competing in sports that emphasise thinness and have a subjective component, such as gymnastics or figure skating, may be at an increased risk for RED-S. (That said, RED-S can also affect non-elite athletes and men.)

How to Use This New Information

Although the study looked only at soccer players, it may contain lessons for runners. While soccer players may have to contend with physical contact from other athletes and frequent cutting that few runners experience, they do run long distances. Some estimates show soccer players run an average of 11 kilometres per game.

The authors of the paper are quick to note that this new information shouldn’t dictate changes in training, but there are some practical takeaways.

Runners should track their menstrual cycles if they’re not already doing so. The American College of Obstetricians and Gynaecologists calls the menstrual cycle a vital sign, and notes monitoring it can alert people to changes or irregularities that could necessitate medical attention. Bassett agrees, saying, “It is something fairly simple that all female athletes can do to potentially decrease their injury risk.”

Knowing when your period is expected can also help you identify when it’s late. In the absence of pregnancy, menopause, or another medical condition, a delayed period can signal RED-S and its accompanying increased risk of injury and other health problems.

Besides noting the length and regularity of their cycle, runners can also try to track their menstrual phase. This can be estimated using time, because ovulation typically occurs 14 days before the start of the following period. It can also be gauged by physical symptoms such as changes in cervical mucous, light cramping, and change in body temperature. While ovulating, cervical mucous becomes more slippery and basal body temperature (measured first thing in the morning) typically rises 0.4-0.8 degrees Fahrenheit. Additionally, ovulation can be identified with ovulation sticks, which detect luteinising hormone, and similar to a pregnancy test, involve placing a stick in urine.

Although there are some privacy concerns, many apps exist that can record and predict your cycle, expected period, and ovulation as well.

Once you begin to track your cycle, you can pair it with your training log to see if you notice any patterns. Perhaps, like Mary Keitany, who was unable to successfully defend her New York City Marathon title in 2017 the day after getting her period, you feel sluggish during your period. Or maybe you tend to sprain your ankle while ovulating. As you begin to compare your cycle with your runs, you may notice themes that emerge over time that can influence the way you structure your training.

Logan agrees that taking your cycle into account with your training is important. “The most impactful thing I can do is create awareness with the athlete, their coach, and their team. The athlete and their coach can best set the training schedule with this knowledge,” she says.

Of course, hormones are only one factor that can influence injury risk. As Bassett says, there are many other things athletes can do to potentially minimise their injury risk, “including maintaining an adequate strength base and flexibility, using proper equipment and having good technique, and avoiding overtraining, as that can lead to a whole subset of overuse injuries.”

Tracking the menstrual cycle is one additional element athletes and their coaches should be aware of. Unlike many another risk factors—such as running in inappropriate shoes—getting your period is relatively unmodifiable. If you’re going to get your period, you may as well try to understand how it affects you and your running.

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