Moderate exercise 'better for sperm' than high intensity exercise
"'Doing at least half an hour of exercise three times a week may boost men's sperm count'," BBC News reports.
Researchers recruited 261 healthy married men who were randomly allocated to three different training programmes. A fourth group did no exercise as a control.
The men's sperm was then tested at various intervals for markers associated with "good fertility", such as sperm count, sperm size and sperm motility (how well the sperm "swim").
The researchers found that all types of training helped improved sperm quality. Moderate-intensity training (around three hours of walking or jogging per week) was found to be the most beneficial.
Importantly, the study did not look at fertility outcomes, so we can't assume the improvements seen in sperm quality would necessarily translate into successful pregnancies.
There are a number of other factors that can improve sperm quality and quantity. Keeping testicles cooler by wearing looser underwear, stopping smoking, cutting down on alcohol, having a healthy balanced diet and being a healthy weight can all help.
If you have been trying to conceive for a year or more and have not had success, see your GP. Your GP can do tests to help identify possible fertility problems and provide advice on the next steps.
Finally, whatever your circumstances, moderate exercise is usually good for your health. Read more about exercise guidelines for adults.
Where did the story come from?
The study was carried out by researchers from Justus-Liebig-University in Germany, Allameh Tabataba'i University in Iran, and the Royan Institute for Reproductive Biomedicine, ACECR in Iran.
The study was published in the peer-reviewed journal Reproduction, on an open-access basis so it is free to read online.
No specific funding was obtained from the public, commercial or not-for-profit sector and the authors declare no conflicts of interest.
The UK media generally reported the story accurately, advising that even for men who start doing a small amount of exercise, sperm quality can improve in as little as six months.
However, suggesting thousands of pounds can be saved by forgoing IVF and taking up running may be a bit misleading as there are many other factors that can affect fertility and the researchers did not look at pregnancy outcomes.
What kind of research was this?
This was a randomised controlled trial which aimed to assess whether exercise of different lengths and intensity had an effect on male reproduction markers.
Previous studies on the link between exercise and sperm quality have come to different conclusions. Some studies have found that strenuous exercise may be harmful for sperm production, while others have found that some exercise might improve semen quality.
Compared with other types of studies, a randomised controlled trial is more likely to show that any effect seen is due to the intervention rather than any confounding variables.
What did the research involve?
The researchers included 261 healthy married men (aged 25-40) from Iran. They excluded people participating in a regular exercise programme or accumulating 25 minutes or more of exercise on most days of the week, or those unable to partake in the physical activity programme.
Participants were randomly assigned to one of four groups:
- Moderate-intensity continuous training (MICT): 12 weeks of walking or jogging on a treadmill 25-30 minutes, 3-4 days/week followed by 12 weeks of 40-45 minutes, 4-6 days/week.
- High-intensity continuous training (HICT): 12 weeks of running 40-50 minutes (involving cycles of 10 minutes moderately fast followed by 3 minutes slow), 3 days/week, followed by 12 weeks of 50-60 minutes, 3 days/week.
- High-intensity interval training (HIIT): 12 weeks of 10 x 1 minute very fast running with 1 minute recovery between each interval, followed by 12 weeks of 15 x 1 minute high intensity intervals with 1 minute recovery between each interval.
- No exercise.
All exercise sessions were performed at the same time of the day and participants were instructed to maintain their normal daily activities and normal diet during the period of study.
Semen analysis was performed at baseline, 12 weeks, 24 weeks and 7 and 30 days after training had finished. The men were advised to abstain from masturbation or sex for three days before providing the sample.
Measurements were taken of:
- semen volume
- progressive motility (swim forward in a straight line)
- sperm size and shape
- sperm concentration
- number of spermatozoa
What were the basic results?
Men in all three exercise groups reduced their body mass index (BMI) and saw improvements in their sperm tests results compared with men in the no exercise group, over the 24 week trial period.
Moderate-intensity continuous training group
In the moderate-intensity continuous training group, progressive motility, sperm shape and size, and sperm concentration significantly improved by 12 and 24 weeks of training compared with baseline. Semen volume and number of spermatozoa were significantly altered after 24 weeks of training compared to baseline. Thirty days after the end of the training programme, the improvements had only been maintained in terms of semen volume and progressive motility.
High-intensity continuous training group
In the high-intensity continuous training group, sperm concentration significantly changed by 12 and 24 weeks of training compared to baseline. Progressive motility and sperm size and shape were significantly changed after 24 weeks of training. None of these improvements lasted 30 days after the training programme ended.
High-intensity interval training group
In the high-intensity interval training group, sperm size and shape, and sperm concentration significantly changed by 12 and 24 weeks of exercise training compared with baseline, but were not sustained by 30 days after the end of the training programme.
No exercise
The group who did no exercise demonstrated no changes in semen quality indicators over the 24 weeks.
At 24 weeks, changes in progressive motility, sperm size and shape, sperm concentration and number of spermatozoa in the moderate-intensity group were significantly greater than in any other group.
How did the researchers interpret the results?
The researchers concluded that "after 24 weeks of MICT, HICT or HIIT" there were "favorable improvements in semen quality parameters and sperm DNA integrity."
They add 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."
Conclusion
This randomised controlled trial indicated doing exercise three times a week may increase sperm quality and count. It showed that undertaking moderate-intensity continuous training was more beneficial than high-intensity continuous training or high-intensity interval training.
All three types of training were more beneficial than no exercise.
The study was well designed and accounted for confounding variables where possible. However, there are some limiting factors to consider:
- One of the reasons for the benefit may be due to losing excess weight – all three training programmes were found to reduce BMI and fat, therefore it may be the lower weight contributing to the sperm quality rather than exercise itself.
- The study was carried out in Iran where there may be diet, cultural and lifestyle factors that might affect sperm quality that are not applicable to populations in other countries.
- The participants all had a history of doing little exercise. This means they may have been less fit and healthy in the first place compared with the general population of 25-40 year old men.
Overall, the study indicates that moderate exercise is conducive to improved sperm quality. However, the exact optimal amount and duration of exercise is unknown, with some research suggesting that participation in very intense competitive sports can lower sperm quality.
Read more advice about improving your fertility and what to do if you or your partner are concerned about your fertility.
