How Your Menstrual Cycle Affects Running

(Author’s Note: This article is an update of a previous article. The previous article explored the concept of adjusting training around the menstrual cycle; the article is now updated to reflect recent scientific literature.)

One theory perpetuated on social media suggests that women experience their best running performance during their period. Theoretically, this occurs due to higher levels of testosterone during menstruation (Sims, 2016). But is that true? Does that apply to every female runner? Are you an anomaly if you feel like hot garbage during your period but crush workouts during PMS?

How Does The Menstrual Cycle Affect Running?

Exercise science is an ever-evolving field – particularly in regards to female athletes. Women are still an underrepresented field in sports science. Additionally, studies done on the impact of the menstrual cycle on athletic performance are still relatively new. 

So, when Dr. Sims published ROAR in 2016, the initial theory was that women performed better during their period and during the follicular phase (between menstruation and ovulation) than they did during their luteal phase (between ovulation and menstruation). However, since 2016, other researchers have studied this topic. And while Sims’ thesis has proliferated across social media, the recent body of research presents a more complicated conclusion. 

In short: we cannot yet definitively say how the menstrual cycle phases affect women’s performance, because the only conclusion from recent literature is that it widely varies based on the individual. 

Now, a few important notes:

• These studies looked at women with normal menstrual cycles. Women on hormonal birth control, amenorrheic women, and women with irregular cycles were not included in these studies. 
• Quality of evidence is important. Systematic reviews and meta-analyses are studies that examine the data and conclusions from many previous studies; therefore they offer a higher level of data than a singular trial study. 
• In exercise science, you ideally want to use research from the past 5-10 years. 
• In exercise science, we are all just working with theories. Theories change and develop. It does not mean someone is “wrong” when they develop a theory with the best information available at the time. What matters is adapting your stances based on the knowledge presented as the field grows.

What Recent Research Says about Menstrual Cycle and Women’s Athletic Performance

One study (Greenhall et al., 2020) surveyed 189 female marathoners. Of those 189, 106 had their best marathon performance during the luteal phase (aka PMS). The other 79 had their best performance during the follicular phase. This certainly contradicts the notion that the luteal phase equates to crappy performance since over half of the women had their best performance during the high hormone phase. The researchers concluded women have individual responses to how their menstrual cycle affects their marathon performance. 

One study on ten female athletes (Goldsmith & Glaister, 2020) found that the mid-luteal phase may decrease running economy during competition in extreme heat/humidity. During the mid-luteal phase, basal body temperature increases, which results in an elevated core temperature. Elevated core temperature can have a negative effect on running economy, particularly if the race conditions are very hot. However, they observed no effect on performance markers (including time to exhaustion!) (Note also: most runners, male or female, will experience a decrease in running economy in hot conditions.)

A systematic review and meta-analysis (McNulty et al, 2020) examined the results of 78 studies (51 for meta-analysis). Their conclusion? “Exercise performance might be trivially reduced during the early follicular phase” – aka right around menstruation/end of menstruation. This is the exact opposite of the theory that the best time to race is on your period. However, this effect was so small that it is meaningless for most athletes. The researchers believe the data is insufficient to prescribe any generalized guidelines. 

Another systematic review (Meignie et al, 2021) found that ultimately, we need further research to be able to actually make evidence-based recommendations for adapting training throughout the menstrual cycle. 

Finally, yet another systematic review (Carmichael et al, 2021) determined no conclusive effect of menstrual cycle phases on performance markers for either strength or endurance. In fact, most studies they reviewed showed no variation of performance throughout the menstrual cycle even when the female athletes believed that their cycle was affecting their performance. 

What the Research Practically Means

Essentially, the research shows that we simply cannot make a conclusion. Any impact of the menstrual cycle on women’s athletic performance is (1) individual and (2) trivial for most (due to the individual variation, some women may experience a significant impact). 

Should You Plan You Training Around Your Cycle?

If you want to, go for it – but know that you have to be an experiment of one. And if adjusting training for your cycle sounds overly complicated, don’t fret. You can train productively without giving your hormones a single thought.

Based on the only conclusion presented by the literature – that any effect of menstrual cycle phases on running performance is individual – you ultimately should adapt based on your own observations. You may find that you feel like hot garbage during your period, thanks to cramps and GI upset. Alternatively, you may observe that your running is unaffected. You may find that you need an extra rest day when your period starts, or when PMS is bad. Or, you may experience ovulation pain that requires scaling back your workout. Observe your own patterns and adjust based on your needs, since that is what the research concludes. Or, it’s not worth your mental energy to even think about how your period affects your running. 

However, do not let the theory that your performance is best on your period and worst in the second half of your cycle dictate your race decisions or mindset. That certainly wasn’t even the intention of Sims, but her message has been pushed that way. It is fatalistic to assume that a race during your luteal phase automatically means a suboptimal performance. Ultimately, you never know until you try – even when you are PMSing or on your period.

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Do you notice differences in your training around your cycle?