Right now, at the 2026 Winter Olympics in Milan and Cortina, female athletes are skiing, snowboarding, and skating at the highest level. Breezy Johnson just won gold in women's downhill. Mikaela Shiffrin is chasing her 108th World Cup victory while competing across multiple Alpine events. Josie Baff took gold in snowboard cross.
These athletes train through their periods. They compete on day one of their cycle and day twenty-eight. The question isn't whether they can perform at an elite level during menstruation. They obviously can. The question is whether hormonal fluctuations across the menstrual cycle affect injury risk.
In January 2026, researchers published a systematic review and meta-analysis in Scientific Reports examining exactly that question. They looked at muscle injuries specifically, the most common injury type in female team sports, occurring roughly 16 times more often than ACL tears.
The findings? More complicated than you'd expect.
What the Research Found
The study pooled data from three research papers tracking muscle injuries in professional female soccer and futsal players across different phases of the menstrual cycle. The researchers divided the cycle into two phases: follicular (menstruation through ovulation) and luteal (ovulation through the next period).
The meta-analysis found no statistically significant difference in muscle injury occurrence between the two phases. The pooled risk ratio was 1.18, meaning injuries were slightly more common in the luteal phase, but not enough to reach statistical significance.
Before you dismiss this as "hormones don't matter," read the rest.
Why We Can't Draw Simple Conclusions
The researchers themselves rated the certainty of this evidence as "very low." Three major problems limited what they could conclude.
First, the studies used self-reported menstrual tracking. Athletes reported when their periods started, and researchers used calendar counting to estimate cycle phases. No blood tests. No urinary ovulation kits. Just counting days.
This method is notoriously inaccurate. Cycle length varies between women and within the same woman across months. Stress, training load, illness, and weight changes all affect ovulation timing. Regular bleeding doesn't guarantee an ovulatory cycle with typical hormone patterns. You can bleed on schedule and still have atypical estrogen and progesterone levels.
Second, studies classified menstrual phases inconsistently. One study divided the cycle into five phases. Another used three. A third used four. To analyze them together, researchers had to collapse everything into two broad categories. That's like trying to understand weather by dividing the year into "warm half" and "cold half." You lose critical detail.
Estrogen and progesterone don't stay constant within the follicular or luteal phase. They peak, drop, and fluctuate. The late follicular phase (high estrogen, low progesterone) is hormonally distinct from early follicular phase (low estrogen, low progesterone). Grouping them together may mask real effects.
Third, confounding factors weren't controlled. Previous muscle injury is the strongest predictor of future muscle injury. Training load matters. Fatigue matters. One of the included studies found that over 60% of injuries happened late in training sessions, when athletes were tired. Another found higher injury rates in the season's first quarter, when training volume spiked.
Did injuries cluster in certain menstrual phases because of hormones, or because high-intensity training coincidentally lined up with those phases? The studies couldn't tell.
What We Know About Hormones and Injury Risk
The biological plausibility is real. Estrogen affects collagen metabolism, tissue compliance, and muscle recovery. Progesterone raises core body temperature and may influence ligament laxity. These are measurable physiological changes.
Research on ACL injuries has shown similarly mixed results. Some studies find higher risk during certain cycle phases. Others find no pattern. Individual variability is massive.
Recent research published this week in WeLoveCycling notes that between-woman differences are often greater than within-woman differences across the cycle. Translation: the variation between two athletes is bigger than the variation one athlete experiences across her own cycle.
That doesn't mean tracking your cycle is pointless. It means universal prescriptions don't work.
What Athletes Should Actually Do
Track your own patterns. Note cycle phase, subjective effort, sleep quality, training load, and how your body feels. Do this for at least three months. Look for patterns specific to you.
Some athletes feel strongest in the late follicular phase. Others notice no difference. Some struggle with high-intensity sessions in the late luteal phase. Others don't. Your data matters more than group averages.
Fuel adequately. Low energy availability disrupts hormonal function, increases injury risk, and worsens bone health. Resting energy expenditure may increase slightly during the luteal phase, along with carbohydrate needs. If you're consistently exhausted the week before your period, underfueling may be the problem, not hormones alone.
Protect sleep. Progesterone raises core body temperature after ovulation, which can reduce deep sleep quality in some women. If sleep disruption coincides with hard training, that's a setup for poor recovery and elevated injury risk.
Adjust training when it makes sense. If you notice a consistent pattern where high-intensity intervals feel disproportionately hard during specific cycle phases, plan accordingly. Move them to phases where you feel stronger, or accept that they'll require more recovery.
Don't use your cycle as an excuse to skip hard training. Hormonal fluctuations are real, but they don't dictate performance. Olympic athletes set personal bests across all cycle phases. The goal is informed adaptation, not avoidance.
The Bigger Picture
The 2026 Scientific Reports study concludes with a recommendation: future research must use direct hormone measurements (blood tests or urinary ovulation kits), standardize phase classification, and control for confounding variables like training load and injury history.
Until that research exists, we're left with incomplete answers. The absence of clear evidence for a menstrual cycle effect on injury risk doesn't mean the effect doesn't exist. It means the studies haven't been good enough to detect it.
Your cycle is one variable in a complex system. It interacts with sleep, fueling, training load, stress, and previous injury history. Tracking it gives you information. Information lets you make smarter decisions.
Train smart. Fuel adequately. Track your patterns. And when someone tells you to take it easy because of your period, ask them to show you the data.
Sources:
Golla, Y., Schmitt, D., & Jäger, R. (2026). The influence of the menstrual cycle on muscle injuries: a systematic review and meta-analysis. Scientific Reports, 16.
"The Reality of Training as a Woman: Hormones, Performance, and What the Research Actually Says." WeLoveCycling, February 13, 2026.
Olympic coverage: NBC Sports, CBS News, Britannica Sports (February 2026)
