Doctors in Austria have warned that mountain biking could make male riders impotent.

Researchers at University Hospital in Innsbruck studied a group of forty-five amateur mountain bikers who cycled at least two hours a day, six days a week.

They found that virtually all of them had scrotal abnormalities, compared to only sixteen per cent of a control group of medical students.

Many of the mountain bikers had developed cysts containing sperm, suggesting that the vibration of their bikes over rugged terrain had damaged their testicles.

The study, published in the British medical journal The Lancet, advised mountain bikers to wear padded shorts and fit padded saddles to their bikes.

From the newsroom of the BBC World Service