Researchers told the European fertility conference that cycle training of the intensity undertaken by triathletes has a significant impact on the quality of their sperm.
But Diana Vaamonde from the University of Cordoba medical school in Spain said she thought the “regular guy” who rides a bike should be fine. “I don’t think he will have to worry about it so long as it’s just like cycling to work,” she said.
Triathletes push themselves to the limit in three sports — running, swimming and cycling.
Professor Vaamonde and colleagues decided to monitor the impact of all three sports on 15 Spanish triathletes to see whether one was more responsible than another. They found that only cycling had a clear correlation with sperm quality, and the more the triathletes trained, the worse it got.
“While all triathletes had less than 10 percent of normal-looking sperm, the men with less than 4 percent — at which percentage they would generally be considered to have significant fertility problems — were systematically covering over 300km per week on their bicycles,” she said.
It may be the irritation and compression caused by friction of the testes against the saddle or the heat caused by tight clothing that causes the problem, but it could also be a function of cell changes connected with the amount of physical energy the cyclists are using.
Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: “It is important to stress that even if the association between cycling and poor sperm morphology is correct, men training for triathlons are spending much more time in the saddle than the average social cycler.”
“There is no evidence that men who ride a bike are less fertile than other males,” he said.