Researchers speaking at a recent European fertility conference told listeners that long hours in the saddle may be linked to infertility. They studied 15 triathletes in an attempt to determine whether swimming, running, or cycling had an affect on sperm count, and found that only cycling had a direct correlation. They also found that the more time a rider spent training, the lower their count. From an article in the Guardian:
While all triathletes had less than 10% of normal-looking sperm, the men with less than 4% — at which percentage they would generally be considered to have significant fertility problems — were systematically covering over 300km per week on their bicycles.
The good news is that average bicyclists riding to-and-from work, or running errands on the weekend, have little to be concerned about:
Allan Pacey, senior lecturer in andrology at the University of Sheffield, said there had been considerable interest among the cycling community in recent years about whether or not too many hours in the saddle might affect male fertility.
“However, 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 or someone who might cycle to and from work,” he said. “There is no evidence that men who ride a bike are less fertile than other males. Indeed, if you look back in our history, only 40 years ago cycling was much more common and there is no evidence from that time that men were less fertile. In fact, quite the contrary! The post-war baby boom proves that.”