Elite Cyclists Risk Losing Fertility

Dr. Randy Morris

Elite Cyclists Risk Losing Fertility

Dr. Randy Morris

Researchers have recently found that professional cyclists should consider the risks involved with the combination of cycling and infertility. In theory, riding a bicycle or motorcycle could cause abnormalities in either sperm concentration, sperm motility or sperm appearance or morphology.

In a recent study, 15 male triathletes around the age of 33 were asked not to have sex for 3 days prior to giving a sperm sample. Semen samples were assessed for morphology by using the Kruger Method. This is also known as strict morphology. In this method for looking at sperm, fertile men typically will have more than 14% of their sperm look “normal”. Some studies have identified fertility problems when men have only between 4 and 14% normal appearing sperm. There is agreement that a normal morphology rate of less than 4% is strongly associated with a decrease in male fertility.

Their semen results of the triathletes were compared with their training routines. Only cycling- not swimming or running- was shown to have an adverse effect on the sperm morphology.

  • Cycling for an average of 9 times/ week for 8 years was linked to <10% normal looking sperm
  • Men that cycled for >186 miles /week were linked to a morphology of 4% normal sperm

What could be causing the problem?

  • Heat from the tight clothing
  • Friction or pressure on the testes from the bicycle seat
  • Stress from the high amounts of energy used during rigorous exercise
  • Increase in free radicals in the male reproductive tract

Researchers are doing further research to investigate how cycling may affect metabolic processes in the body which lead to the development of abnormal sperm.


In order to avoid fertility problems, elite cyclists could consider several options

  • Decreasing the time actually on the bike
  • Freezing sperm before any problems occur
  • Antioxidants – to reduce the levels of free radicals
  • Modify training regimens to adjust for recovery

Unfortunately, there is no data to indicate whether any of these measures will have a positive impact of sperm morphology in these cyclists.

Don't Worry!

The average man bicycles for recreation only would be unlikely to suffer from fertility problems. Only extremely high levels of exercise and cycling may contribute to decreased sperm quality. Men training for triathlons are spending a lot more time on their bikes than average.