Getting Injured Is Much More Dangerous When You’re on Your Period

Recovery took three times longer.

Women footballers hurt their knees much more often than men. It is a statistical fact that haunts the sport. For years, researchers have tried to figure out why, looking at everything from boot design and artificial turf to training regimes.

Then, there is the menstrual cycle. The theory makes sense: hormones ebb and flow, creating biological tides that could leave the body more exposed at certain times of the month.

But a groundbreaking four-year study from inside the medical department of FC Barcelona, one of the world’s best football teams, gives that theory a massive spin. The data suggests that players were not statistically more likely to get injured while on their periods. However, when they did get injured while menstruating, the outcome was much worse. The number of days lost to rehabilitation was more than three times higher during menstruation compared to the rest of the cycle.

Queens of the Pitch

Recent media attention has brought more fans than ever to women’s football. It’s estimated that by 2030, it will become a top 5 global sport with over 800 million fans. Yet, despite the hype, the science of welfare for these athletes is lagging dangerously behind.

This is where the new study comes in. The medical department at FC Barcelona tracked 33 elite players from 2019 to 2023. In that period, the team won two UEFA Women’s Champions League titles, making them arguably the world’s strongest club team.

Overall, the researchers tracked 852 menstrual cycles and 80 time-loss injuries over four years. For football teams, these “time-loss” injuries are extremely important. In addition to the recovery itself, every day an athlete spends off the pitch can cost the club dearly.

The researchers used a relatively crude method. They divided the cycle into two simple camps: the “bleeding phase” (menstruation) and the “non-bleeding phase”. This lacks the nuance of identifying ovulation or other hormonal peaks, but it’s reliable. You know when you are bleeding. Plus, other methods would have required a more invasive monitoring process. At the same time, the club’s doctors recorded any injuries that occurred, categorizing them using a standard scale.

There’s been a long-standing fear that the period is a “danger zone” for injury occurrence. The Barcelona data says: Not really. During the bleeding phase, the injury rate was 5.46 per 1,000 hours of exposure. During the non-bleeding phase, it was 6.60. Technically, they got hurt slightly less often while menstruating, though the difference wasn’t statistically significant.

But the severity of the injuries was very different.

A Much Higher Burden

During non-bleeding days, there were 206 days lost to injuries per 1,000 hours of exposure. During bleeding days, it was 684 days, over three times higher. The injuries were way worse. Ligament tears. Severe muscle strains. The kind of injuries that end seasons. Granted, there were fewer cases to study during menstruation, but the difference is striking.

Why is this happening? The reason could be estrogen.

Estrogen is often described as a simple “sex hormone,” but it plays an important role in musculoskeletal health. It has a protective effect on muscles and tendons. It helps with repair; it helps with strength. During the menstrual phase (the early follicular phase), your ovarian hormones hit rock bottom. Estrogen and progesterone concentrations are low. The biological shield is down.

Without that hormonal buffer, the body reacts differently to stress. The study authors point out that low estrogen is linked to increased susceptibility to muscle damage and higher inflammation. If you tear a muscle when estrogen is high, your body might snap back quickly. Tear it when estrogen is low, and the recovery drags. The tissue is more vulnerable, and the repair mechanisms are sluggish.

But there could be other factors at play. If an athlete is losing blood (and iron), she is fighting fatigue. If she is in pain from cramps, her neuromuscular control might be slightly off. In elite sport, where the margins are thin, a delay of a fraction of a second could make a big difference.

What Do We Do With This Info?

The authors admit limitations for this study. They couldn’t measure daily hormone levels because, well, they had a Champions League to win. Also, the experiences of elite athletes may not be representative for other people. However, this study helps to fill a huge gender data gap.

For decades, sports science has failed women. We’ve had plenty of studies on how caffeine, creatine, or various factors affect male athletes, and far less for women. The gap is still huge, but studies like this help chip away at it.

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If you’re the coach of a female team, this doesn’t mean you bench players because they are on their periods. That’s the wrong takeaway. The injury incidence wasn’t higher, and menstruating athletes can still play. They can still win.

But their risk is higher.

If the “injury burden” is higher during the bleed, recovery protocols need to be dialed in. This is the time to prioritize sleep and nutrition. Iron intake becomes critical to combat the losses from bleeding.

Also, the study suggests that individualized tracking is non-negotiable. If a player is menstruating and reporting high symptom severity (cramps, fatigue), maybe that’s not the day for maximum-load plyometrics. It might be the day to focus on tactical work or lower-impact drilling.

As for everyone else, it’s an important reminder: women’s bodies change during the menstrual cycle. During some periods, particularly when bleeding, the risk can be much higher.

The study was published in Frontiers in Sports and Active Living DOI: 10.3389/fspor.2025.1665482.