Spanish researchers found that triathletes who cycled more than 180 miles a week had significantly lower levels of healthy sperm. They suggest that cyclists who undergo high-intensity training regimes may need to take measures to protect their fertility.
What is the research?
University of Cordoba researchers analysed semen samples and training patterns of 15 male triathletes aged 29 to 36.
They found that the number of weekly miles cycled by the men was inversely related to the proportion of healthy sperm in their semen samples.
For men covering more than 180 miles a week under 4 per cent of their sperm were normal, a level at which they would be considered to have significant fertility problems. Neither running nor swimming training showed a clear correlation with sperm quality. The researchers suggest that sperm may be damaged by irritation or warming of the testes during cycling.
What do the researchers say?
Professor Diana Vaamonde, from the University of Cordoba Medical School, who led the study, said that protective measures need to be developed for cyclists covering long distances.
'Depending on the mechanism leading to the creation of abnormal sperm, these could include giving antioxidants and modifying training regimes to allow for recovery,' she said. 'Or we could take preventive measures by freezing athletes' sperm before they start high intensity training.'
She added: 'We believe that we have uncovered a serious problem affecting triathletes who undertake significant amounts of training, and we hope that our research may lead to effective treatment.'
What do other researchers say?
Dr Allan Pacey, a fertility expert at Sheffield University and secretary of the British Fertility Society, said that any problems were unlikely to affect those cycling relative short distances.
'There is a big difference between a triathlete and someone who might cycle to work,' he said.
'For the average cyclist travelling to work, I wouldn't worry about it, although for triathlon professionals and obsessive sportsmen it might be an issue.'
- Researchers studied triathletes undertaking intense training
- Cycling over 180 miles a week damages sperm
- Problems unlikely for cyclists covering shorter distances