Exercise and irregular periods

When exercise helps regulate your cycle

Moderate exercise (150 minutes per week of walking, swimming, cycling, or light strength training) improves hormonal balance. It reduces excess cortisol, improves insulin sensitivity, and helps maintain a healthy body composition. All of these support regular ovulation.

For women with PCOS (the most common cause of irregular periods), exercise is one of the most effective interventions. A 2019 study in Human Reproduction found that women with PCOS who did 3 hours of moderate exercise per week had significantly more regular cycles after 6 months.

When exercise causes irregularity

Too much intensity or too little body fat and your period disappears. This is called hypothalamic amenorrhea, and it happens when your brain decides conditions aren't safe for reproduction.

The threshold varies by person, but common triggers: training more than 10 hours per week, being in a caloric deficit for extended periods, or having body fat below ~17-19%.

This isn't healthy. Missing your period from overtraining means your estrogen is tanked, which affects bone density, heart health, and mood. If your period has disappeared and you're training hard, please talk to a doctor. This isn't about being tough.

The sweet spot

3-5 workouts per week. Mix of strength and cardio. Eating enough to support your activity level. Getting 7+ hours of sleep.

Boring advice. Also true.

If your period has been irregular and you start exercising moderately, give it 2-3 months. Hormonal changes from exercise take time to show up in your cycle. Don't expect results in two weeks.

Tracking helps

Log your workouts alongside your cycle for 3 months. Note cycle length, symptoms, and training intensity. You'll see whether your training is helping or hurting.

Apps like Lune do this automatically. They track your cycle and adjust your workout intensity so you're not accidentally overdoing it during phases when your body needs rest.