Endurance cyclists are known for their peak fitness, yet scientific research reveals that many male cyclists face surprisingly low sperm counts. Similarly, ultra-fit marathon runners are experiencing declines in reproductive health. Studies indicate that super-fit professional athletes often have lower sperm counts compared to “ordinary” men. Why are these ultra-fit individuals facing fertility issues, and what steps should athletic men take – or avoid – to protect their fertility?

Below are six simple but effective strategies to help all male endurance athletes stay fit and fertile.

Also in our Male Infertility special investigation

• Sperm counts in freefall: is the male infertility crisis an existential threat to humanity?
• “Are men facing a terminal decline in testosterone?”
• 10 ways men can boost their fertility
• Can too much endurance exercise make you infertile?

1. Stick to a regular workout regime

Just half an hour of exercise, three times a week, can boost a man’s sperm count, according to research in the journal Reproduction. But make sure your exercise regime is consistent. The same study found that men who stuck with their workouts maintained their volume of healthy sperm. But when men stopped training, the health of their sperm began to wane within a month.

2. Enjoy stamina sessions in moderation

There is nothing wrong with taking on the occasional endurance challenge, or enjoying long workouts in moderation. But extreme cycling, marathon and triathlon training can negatively affect your sperm health if the volume becomes excessive. A study in Andrology found that recreational athletes who trained for 4-5 hours per week had healthier semen production than elite athletes who trained 4-5 days per week.

3. Limit your high-intensity workouts

High-intensity workouts are great for your cardiovascular health, but don’t make every workout a sweat-fest. Research suggests that cranking up the intensity too often can affect your sperm health. One study in the Journal of Endocrinology found that excessive workouts above 80% VO2 max can affect a man’s sperm health. Sprinkle in a few high-intensity workouts throughout the week, but balance them out with medium-intensity and low-intensity sessions too.

4. Lift weights

Moderate-intensity weight training is linked to higher sperm concentrations, according to a 2014 study in Human Reproduction, though not necessarily enhanced reproductive success. Weight training increases levels of free and total testosterone levels and improves insulin sensitivity to help optimise sperm production.

5. Don’t lose too much weight

Research has shown that men with a high BMI – over 25 – have poorer sperm health. But a study in Fertility and Sterility found that men with a BMI below 20 had a 28.1% reduction in sperm concentration and a 36.4% reduction in total sperm count. Athletes who train too hard can quickly become underweight, so try to maintain a healthy BMI. As a general rule, the NHS defines a healthy BMI as 18.5-24.9.

6. Take it outside

The same study found that outdoor exercise activities were associated with higher sperm concentrations. This was an unexpected find, and the researchers believe this may be because training outside enhances vitamin D production. Research has shown a link between vitamin D and testosterone – a key hormone for sperm production.