For male bicyclists, the road to fatherhood may have just hit a few more bumps.
Two studies in as many months add to recent evidence that bicycling can be hazardous to a man's reproductive health -- especially for dedicated mountain bikers. One, released a few weeks ago, found that frequent mountain bike riding can lower sperm counts, damage the scrotum and possibly reduce fertility. The other, published in November, showed that even less strenuous cycling can cause genital numbness and interfere with erectile function.
Studies suggesting a troubling link between cycling and procreation have been steadily surfacing since a prominent urologist asserted five years ago that bicycling has caused at least 100,000 men to become impotent, and the latest research is sure to add to debate among cyclists and physicians.
"Biking overall is a great sport," said Dr. Ferdinand Frauscher, who presented the most recent findings at a conference of the Radiological Society of North America. "It's excellent exercise for the cardiovascular system, but like other sports -- like skiing and running -- it carries a certain set of risks."
But not even the latest findings, serious though they are, probably will knock the millions of cycling men off their bikes. Not only are doctors reluctant to discourage the activity, particularly when done in moderation, the cycling industry has developed new designs that can mitigate whatever potential harm may exist.
Frauscher's study compared 40 mountain bikers with 35 non-cyclists over one year and found that 90% of the cyclists who rode more than 3,000 miles a year produced one-third the sperm and had much lower sperm motility and volume compared with non-cyclists. The cyclists, too, were almost four times as likely to exhibit scrotum abnormalities, including cysts, calcifications and varicose veins.
"We believe the microtrauma from shocks and vibrations are the major reason for the resulting testicular vascular damage," said Frauscher, a uroradiologist at University Hospital in Innsbruck, Austria.
The other study, published last month in the Journal of Andrology, followed a group of 17 bicycle police in Long Beach and found that they had erections for less time during sleep compared with non-riders. The study was done by the Centers for Disease Control and Prevention and the National Institute for Occupational Safety and Health.
Both studies cited the bicycle seat, or saddle as bikers refer to it, as the chief culprit. The more time on the bike, the more likely there would be a problem. The saddle's nose often puts extra pressure on the perineum, the area behind the scrotum, where nerves and arteries run to the genitals.
Many bicyclists -- backed by some physicians -- say the recent studies overstate the risks. They point to countries such as China, where a vast majority of men bicycle and don't experience above-normal rates of infertility or sexual dysfunction. Also, they say, fertility difficulties pale in comparison to the well-known risks of remaining sedentary, a practice that contributes to obesity, diabetes and heart ailments.
But even the most enthusiastic cyclists concede the saddle can be a real pain. Cyclists say the key to finding a good one is trial and error and learning to make small angle adjustments.
"The saddle is the worst part of the bike, always has been, always will be," said Jim Hasenauer, a board member of the International Mountain Bicycling Assn. and a Woodland Hills resident. "I know guys whose garages are full of saddles. It can be like trying to find the holy grail."
In recent years, bicycle manufacturers have created dozens of new ergonomically designed saddles, which more evenly distribute a rider's weight, promising comfort and alleviating pressure on the perineum.
So far, the seats, which offer more padding or feature a triangle-shaped wedge cut out of its middle, have received positive reviews. In the case of mountain biking, doctors say the seats -- when combined with a full suspension system -- can go a long way in warding off any potential fertility problems. Full suspension systems function like shock absorbers on a car and create a smoother ride.
But there are a couple of reasons some bikers balk at the improvements. The first is cost. The new generation of saddles can run $45 to $100, while full suspension can add as much as $150 to $600 to the overall price. Also, saddles tend to be heavy and would add burdensome extra weight to the bicycle.
If the precautions are taken, however, there's no reason to abandon cycling for fear of not being a father, said Frauscher, himself a mountain biker.