Reproductive experts have found in a study that intense cycling training produces more abnormal sperm among avid triathletes giving them higher risk of suffering from infertility.

The more cycling training triathletes undertake in terms of time and distance, the worse their sperm quality became, according to the study team led by Professor Diana Vaamonde, from the University of Cordoba Medical School in Cordoba, Spain.

Citing a study of semen values of 15 healthy Spanish triathletes, with an average age of 33, Sciencedaily.com quoted Vaamonde as telling attendees to Monday's 25th annual conference of the European Society of Human Reproduction and Embryology that while all triathletes had less than 10 percent of normal-looking sperm, the men with less than four percent - at which percentage they would generally be considered to have significant fertility problems - were systematically covering over 300 kilometers (186 miles) per week on their bicycles.

Vaamonde blamed the sperm anomaly to either the irritation and compression caused by friction of the testes against the saddle, or the localized heat produced by wearing tight clothing. However, her study team will conduct more research to determine the exact cause of the sperm abnormality.

Vaamonde suggested protective measures such as giving triathletes antioxidants, modifying their training regimes to allow for recovery or preserving their sperm before training.