Cycling in male infertility link
Updated on 29 June 2009
Men who are too passionate about cycling could be pedalling their fertility away, it has been claimed.
Scientists who studied a group of triathletes found the more they cycled the more damaged their sperm became.
Those who covered more than 300 kilometres a week had less than 4% "normal" sperm.
They were likely to be suffering "significant fertility problems" which could become permanent. But the hazard did not just apply to superfit triathlon athletes, said study leader Professor Diane Vaamonde, from the University of Cordoba in Spain.
"We think all professional cyclists, and even people who are not professional but undergo high intensity or high volume cycling, could also suffer from these changes," said Prof Vaamonde, speaking at the European Society of Human Reproduction and Embryology (Eshre) annual meeting in Amsterdam.
The effects were so serious she thought men taking up high-level cycling should consider freezing their sperm before getting on their bikes.
Prof Vaamonde's team analysed the semen of 15 Spanish triathletes with an average age of 33. The more cycling training they undertook the worse their sperm quality became. The researchers looked at the shape and form of the men's sperm after three to six days of sexual abstinence.
Prof Vaamonde said: "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 300 kilometres per week on their bicycles."
Expert Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: "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. There is no evidence that men who ride a bike are less fertile."
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