If you’ve ever felt a bit off during a run—slightly less stable on the trails or slower to react on a descent—it might not be in your head. For runners especially, knee injuries can happen without warning, especially during high-intensity sessions, or when terrain gets tricky. Now, new research is digging into whether the natural hormonal shifts of the menstrual cycle could be quietly increasing the risk for female runners, Women’s Health recently reported. Here’s what you need to know.
Is your cycle putting you at risk?
Turns out, your period might be doing more than messing with your mood, or affecting your mileage. Researchers are starting to ask whether certain phases of the menstrual cycle could quietly raise your risk of injury, specifically, those dreaded ACL (anterior cruciate ligament) tears that can take runners out for months.
The numbers are hard to ignore: women are three to six times more likely than men to suffer ACL injuries, and the rate hasn’t budged in more than two decades. Now, sports scientists at Kingston University in the U.K. are digging into why, and tracking hormone levels and athletic performance throughout the menstrual cycle to see if there’s a pattern.
As biomechanics expert Simon Augustus puts it, “We want to examine whether athletes may be more predisposed to injuries because of functional changes during the menstrual cycle.” Translation: it might not just be bad luck. Your hormones could be affecting how your body moves—and whether it holds up.
How this affects runners
Runners don’t typically twist and pivot like soccer players, but the risk remains, particularly for those who train hard year-round. ACL injuries in running often occur on unstable terrain or during fast turnover, where stability is compromised. Combine this with hormonal phases where ligaments may be more elastic and reaction times slightly slower, and you’ve got a recipe for trouble.
It’s not just elite athletes at risk. The FIFA-backed research is also studying grassroots and amateur players, which means everyday runners stand to benefit from the findings.
What you can do now
We don’t yet have concrete guidelines based on menstrual phases, but awareness is a good first step. If you know you’re in a high-hormone phase (around ovulation, when estrogen peaks), it might be smart to add extra warmups, emphasize proper landing mechanics, or swap speed for strength work.
Better yet? Strengthen your glutes, hamstrings and core year-round to support your knees, no matter where you’re at in your cycle. Many ACL injuries happen without contact, and those are the ones we might actually be able to prevent.
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