Dedicated male triathletes could require infertility treatment if they cycle long distances on a regular basis, doctors have warned.
Presenting their findings at a conference held by the European Society of Human Reproduction and Embryology, a team of scientists from Cordoba Medical School revealed that triathletes who cover more than 186 miles a week on their bikes suffer from significant drops in sperm quality.
Indeed, the proportion of sperm that was found to be of the correct size and shape of those male cyclists analysed stood at just four per cent, compared to a level of between 15 and 20 per cent in normal, fertile men.
As a result, these men would be likely to suffer from "significant fertility problems", study leader Professor Dina Vaamonde from the Spanish university explained.
As well as the time spent up against the saddle, the tight clothing worn by triathletes was also cited as a major reason behind the relative lack of healthy sperm.
However, Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, has advised that this problem is unlikely to affect social cyclists, or even those men who ride their bikes to work on a regular basis.