Does exercise affect fertility – how much is enough?

Short answer: Moderate, regular physical activity does not appear to impair fertility and can benefit both general health and weight. The evidence that hard, very intensive exercise reduces the chance of becoming pregnant is limited and somewhat contradictory. In men, several studies suggest that physical activity is linked to better reproductive health. Prolonged sitting may be unfavorable.

What the research actually shows

The link between exercise and fertility is less well-understood than many believe. A systematic review published in the Journal of Physical Activity and Health in 2023 reviewed 34 studies and concluded that the association between physical activity and spontaneous fertility remains unclear. Of the 25 studies concerning women, most showed either mixed results or no association at all.

This does not mean that exercise is irrelevant – it means that the research evidence is too disparate to draw definitive conclusions. Studies measure activity in different ways, follow different groups, and take different factors into account, such as weight, age, and underlying diagnoses.

Moderate activity versus strenuous exercise

A meta-analysis of prospective cohort studies, published in Frontiers in Public Health in 2022, specifically investigated intensity. It found no association between moderate physical activity and fertility (OR 1.09; 95% CI 0.98–1.22), while high-intensity activity was linked to slightly lower fertility (OR 0.84; 95% CI 0.70–1.00).

Worth noting: the confidence interval for high-intensity activity borders on 1.00, meaning the result is uncertain and close to the threshold for statistical significance. Furthermore, these are observational studies, which can show associations but not prove cause and effect. The conclusion should therefore be read as a signal to be aware – not as a definitive statement that strenuous exercise makes you infertile.

What is better established is the link via body weight and the menstrual cycle. According to 1177 Vårdguiden (Sweden's national health information service), both underweight and overweight can make it more difficult to conceive, as ovulation may not occur. For those who exercise very strenuously in combination with low energy intake, the cycle can be affected – in such cases, it is the energy balance rather than the exercise itself that is the central factor.

Sedentary lifestyle – the other side of the coin

The discussion often focuses on exercising too much, but little research has looked at the opposite. In the 2023 review, seven studies examined sedentary behavior and female fertility, and two of them found that a high amount of sedentary time was linked to lower fertility. The evidence is thus thin, and the authors describe the area as largely unexplored.

The same meta-analysis from 2022 also looked at sleep and found that short sleep (7 hours or less) was weakly linked to lower fertility compared to 8 hours (OR 0.92; 95% CI 0.84–1.00). Here too, the uncertainty is great, but it suggests that recovery may be at least as relevant as the amount of exercise.

Exercise and male fertility

The picture is somewhat clearer on the male side. In the 2023 review, 11 studies concerned men, and six of them found that physical activity was linked to better fertility. Here too, the studies differ in design, so the results should be interpreted cautiously.

1177 Vårdguiden also highlights that sperm quality can be impaired by overweight, which provides another indirect reason for regular movement. For those who want to read more about what a sperm test measures, there are more articles on this blog.

How to think in practice

Based on current knowledge, regular, moderate movement is a reasonable choice for most people trying to conceive – it supports weight, blood sugar regulation, sleep, and stress management without the evidence indicating any disadvantage for fertility.

If you train hard and at the same time notice that your periods become irregular or stop, it is a reason to contact healthcare providers, rather than stopping exercise on your own. Missed periods are a symptom that should be investigated regardless of the cause. And for those who already exercise a lot and have a regular cycle, there is currently no strong evidence that you need to cut back.

Frequently Asked Questions

Can I continue to exercise as usual when I am trying to conceive?
For most people, current evidence suggests that moderate, regular exercise is fine to continue. If you exercise at an elite or very high level, or have irregular periods, it may be worth checking with a midwife or doctor.

Is strength training worse than cardio for fertility?
We do not know. The existing research primarily distinguishes between intensity and amount, not type of exercise. We have not found evidence that points out any particular type of exercise as better or worse.

Can exercise help with PCOS?
Physical activity is often included in the lifestyle advice given for PCOS, partly linked to insulin sensitivity and weight. The evidence varies between studies, and advice should be individually adapted in consultation with healthcare providers.

This article contains general information and is not medical advice. Always consult a midwife, doctor, or other healthcare professional for questions about your own health, fertility, or treatment.

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