Get your leg over

Look at all those rippling bodies in tight lycra shorts and tops on the Tour De France and you can't deny that cycling is a sexy sport. And not just for spectators. The more you exercise the more libido levels increase, while the cardiovascular workout of cycling raises energy levels and stamina - useful tools in the bedroom.

But experts are divided on the dangers to cyclists who notch up the miles, citing the risk of impotence in men and genitourinary complaints in women.

Dr Irwin Goldstein, of the Boston Medical Centre, who first reported his findings in a 1997 study, says that sitting on a bike seat places the entire body weight on the artery that supplies the penis, inhibiting the blood flow. This is known in the biking world as 'numb nuts' syndrome.

Don't deflate

Goldstein believes it can narrow the artery to the extent it can lead to impotence and infertility. He is adamantly anti-bicycle. 'Men should never ride bicycles. Riding should be banned and outlawed,' he says. 'Every time you hop on a bike you put your sex life on the line.'

His sentiments have been backed up this year by a study from University Hospital, Brussels, which found male cyclists were twice as likely to experience 'erectile dysfunction' as men who never rode bikes.

Goldstein doesn't let women off the hook either. He reports a similar numbness and chaffing which he says can cause 'diminished sexual lubrication and arousal, unsatisfying orgasms, even arthritis'.

His main gripe is saddles. Generally too narrow and thin, they don't give adequate protection against painful jolts and vibrations, he says. Those most at risk are mountain bikers riding on rough terrain. Researchers at University Hospital, in Innsbr¸ck, found scrotal abnormalities in mountain bikers who were in the saddle two hours a day, six days a week.

But help is at hand. Cycle manufacturers have responded with new ergonomic seats designed to relieve groin pressure. Californian doctor Roger Minkow has teamed up with Specialized to create his Body Geometry wedge-shaped seats, to take the pressure off the crotch and on to your bottom.

An end to razor saddles

Weight should be carried on the sitting bones rather than the pubic area, says Hannah Reynolds, coaching editor of Cycling Weekly. She rejects Goldstein's argument as scare-mongering.

'Most cyclists say that the fitness provided by cycling is good for their sex life,' she says. 'Look at Chris Boardman, who has fathered children without any problems. Some people will experience numbness but for the most part it's weekend warriors riding a naff old bike with a poor fit and poor saddle.

Most problems can be solved by a visit to your local bike shop.'

In a curious twist of history, the subject of cycling and sex a century ago
was also a hot topic. The problem then was not that cycling diminished arousal but was seen to encourage it.

In the 1890s opponents to women cyclists saw the saddle as a threat to sexual purity. One doctor said: 'The saddle can be tilted in every bicycle as desired. In this way a girl could bring about constant friction over the clitoris and labia. This pressure would be much increased by stooping forward, and the warmth generated from vigorous exercise might further increase the feeling.'

Today's studies also show a positive link between sex and cycling. They show the vigorous aerobic activity of cycling releases endorphins and other sex hormones including testosterone.

That should enable those who cycle to carry on their aerobic activity in the bedroom, too.