Men could boost the quality of their sperm by exercising three to five times a week, research suggests.

Running or jogging for up to 45 minutes during each training session may boost the volume of sperm as well as its motility and concentration in just a few months.
Researchers asked 261 healthy men aged 25 to 40 who led a sedentary lifestyle to take part in the study.

They were split into groups, with the first group taking part in moderate intensity continuous training (MICT). For the first 12 weeks, men in this group walked or jogged on a treadmill for 25 to 30 minutes per day, three or four times a week.
During the next 12 weeks, they increased this to 40 to 45 minutes per session at a slightly higher intensity, for four to six sessions a week.

The second group of men took part in high intensity continuous training (HICT), running on a treadmill three times a week for 40 to 50 minutes at a time. Each running cycle consisted of 10 minutes at quite a high intensity followed by three-minute intervals of lower intensity. This cycle was repeated four times within each exercise session.

For the final 12 weeks of training, the men undertook three sessions a week, each consisting of 10 minutes of running at quite high intensity followed by three minutes at a lower intensity. This cycle was repeated five times within each exercise session.

The third group of men had three sessions a week for 24 weeks of high intensity interval training (HIIT). During the first 12 weeks, they ran for one minute at their highest speed, followed by one minute of recovery at a much lower speed, repeated 10 times. During the last 12 weeks, this was increased to 15 times per session.

A fourth group of men did no exercise.

The results of the study, published in the journal Reproduction, showed that men who exercised had improved sperm at the end of the training, regardless of which group they were in.

But those men who took part in MICT had the best results.

Compared to men who did no exercise, those in the MICT group had 8.3% more semen volume, 12.4% higher sperm motility, 17.1% improved sperm cell shape, 14.1% more concentrated sperm and 21.8% more sperm cells on average.

The researchers, from Urmia University in Iran, concluded that exercise can improve markers of oxidative stress, which is linked to things such as smoking and unhealthy lifestyles and can damage sperm.

They said: "The present study adds to this body of evidence and shows seminal markers of inflammation and oxidative stress improved significantly after 24 weeks of MICT, HICT or HIIT, and these changes correspond with favourable improvements in semen quality parameters and sperm DNA integrity.
"These results further indicate that MICT was more beneficial in improving markers of male reproductive function, compared to HICT and HIIT. These observations suggest that the intensity, duration and type of exercise training could be taken into consideration when investigating reproductive responses to exercise training in men."
The researchers found that the benefits for sperm started to tail off within just a week of stopping the exercise programme.
Lead author of the study, Behzad Hajizadeh Maleki, said: "Our results show that doing exercise can be a simple, cheap and effective strategy for improving sperm quality in sedentary men.

"However, it's important to acknowledge that the reason some men can't have children isn't just based on their sperm count. Male infertility problems can be complex and changing lifestyles might not solve these cases easily."

Allan Pacey, British Fertility Society spokesman and professor of andrology at the University of Sheffield, said: "We have a very poor understanding of how physical exercise affects male fertility and sperm quality, but it is a question commonly asked by men wishing to improve their chances of having a child.

"We know at one end of the scale, men with sedentary lifestyles have poorer sperm quality than men who undertake regular exercise whereas, at the other end, we know that men who train very hard have poorer sperm quality than men who undertake moderate exercise. Therefore, there is probably a level of exercise associated with optimum levels of male fertility, although that is poorly defined.

"In this context, the study makes a good contribution to the knowledge base. It is a very well conducted and a strength is that it is a randomised controlled trial with extensive data collection. Also, the study examines how exercise affects many of the parameters of male reproductive health, not just sperm quality.

"However, what is likely to be of most interest to men and their doctors are the results concerning sperm quality. Importantly, these seem to show a statistical improvement to various degrees when the men embarked on their different exercise regimes compared to men who did no exercise at all.

"However, an important question is whether these statistical changes are enough to be of any clinical significance. Unfortunately, this is questionable and it would need more research to be carried out to determine if men who exercised were more likely to become dads either naturally or with some form of assisted conception."
Dr Pacey said men could take other steps to boost their fertility and general health, including following a healthy diet, stopping smoking and wearing loose underwear.