"We make kids wear helmets and knee pads," Dr. Goldstein said. "But no one thinks about protecting the crotch."
A raft of new studies suggest that cyclists, particularly men, should be careful which bicycle seats they choose.
The
studies add to earlier evidence that traditional bicycle saddles, the
kind with a narrow rear and pointy nose, play a role in sexual
impotence.
Some saddle designs are more damaging than others, scientists say.
But even so-called ergonomic seats, to protect the sex organs, can be
harmful, the research finds. The dozen or so studies, from
peer-reviewed journals, are summarized in three articles in September's
Journal of Sexual Medicine.
In a bluntly worded editorial with
the articles, Dr. Steven Schrader, a reproductive health expert who
studies cycling at the National Institute for Occupational Safety and
Health, said he believed that it was no longer a question of "whether
or not bicycle riding on a saddle causes erectile dysfunction."
Instead, he said in an interview, "The question is, What are we going to do about it?"
The
studies, by researchers at Boston University and in Italy, found that
the more a person rides, the greater the risk of impotence or loss of
libido. And researchers in Austria have found that many mountain bikers
experience saddle-related trauma that leads to small calcified masses
inside the scrotum.
This does not mean that people should stop cycling, Dr. Schrader
said. And those who ride bikes rarely or for short periods need not
worry.
But riders who spend many hours on a bike each week should
be concerned, he said. And he suggested that the bicycle industry
design safer saddles and stop trivializing the risks of the existing
seats.
A spokesman for the industry said it was aware of the issue and added that "new designs are coming out."
"Most
people are not riding long enough to damage themselves permanently,"
said the spokesman, Marc Sani, publisher of Bicycle Retailer and
Industry News. "But a consumer's first line of defense, for their
enthusiasm as well as sexual prowess, is to go to a bicycle retailer
and get fitted properly on the bike."
Researchers have estimated
that 5 percent of men who ride bikes intensively have developed severe
to moderate erectile dysfunction as a result. But some experts believe
that the numbers may be much higher because many men are too
embarrassed to talk about it or fail to associate cycling with their
problems in the bedroom.
The link between bicycle saddles and
impotence first received public attention in 1997 when a Boston
urologist, Dr. Irwin Goldstein, who had studied the problem, asserted
that "there are only two kinds of male cyclists - those who are
impotent and those who will be impotent."
Cyclists became angry
and defensive, he said, adding: "They said cycling is healthy and could
not possibly hurt you. Sure you can get numb. But impotent? No way."
The
bicycle industry listened, said Joshua Cohen, a physical therapist in
Chapel Hill, N.C., and the author of "Finding the Perfect Bicycle
Seat." Manufacturers designed dozens of new saddles with cut outs,
splits in the back and thick gel padding to relieve pressure on tender
body parts.
Scientists also stepped up their research. Since
2000, a dozen studies have been carried out using sophisticated tools
to see exactly what happens when vulnerable human anatomy meets the
bicycle saddle.
The area in question is the perineum, between
the external genitals and the anus. "When you sit on a chair you never
put weight on the perineum," Dr. Schrader said. "But when you sit on a
bike, you increase pressure on the perineum" sevenfold.
In men,
a sheath in the perineum, called Alcock's canal, contains an artery and
a nerve that supply the penis with blood and sensation. The canal runs
along the side of a bone, Dr. Goldstein said, and when a cyclist sits
hard on a narrow saddle, the artery and the nerve are compressed. Over
time, a reduction of blood flow can mean that there is not enough
pressure to achieve full erection.
In women, Dr. Goldstein said,
the same arteries and nerves engorge the clitoris during sexual
intercourse. Women cyclists have not been studied as much, he added,
but they probably suffer the same injuries.
Researchers are using a variety of methods to study the compression
caused by different saddles. One method involves draping a special pad
with 900 pressure sensors over the saddle. The distribution of the
rider's weight is then registered on a computer. In another technique,
sensors are placed on the rider's penis to measure oxygen flowing
through arteries beneath the skin. Blood flow is detected by other
sensors that send a "swoosh" sound to a Doppler machine.
The research shows that when riders sit on a classic saddle with a
teardrop shape and a long nose, a quarter of their body weight rests on
the nose, putting pressure on the perineum. The amount of oxygen
reaching the penis typically falls 70 percent to 80 percent in three
minutes. "A guy can sit on a saddle and have his penis oxygen levels
drop 100 percent but he doesn't know it," Mr. Cohen said. "After half
an hour he goes numb."
Dr. Goldstein added, "Numbness is your body telling you something is wrong."
Today's
ergonomic saddles have splits in the back or holes in the center to
relieve pressure on the perineum. But this may make matters worse: the
ergonomic saddles have smaller surface areas, so the rider's weight
presses harder on less saddle, Dr. Schrader said. The perineum may not
escape injury because its arteries run laterally and they are not
directly over the cutouts. The arteries can come under more pressure
when they come into contact with the cutouts' edges.
Thick gels
on saddles can also increase pressure to the perineum, the studies
found, because the material can migrate and form clumps in all the
wrong places.
Just as many smokers do not get lung cancer,
many cyclists will never develop impotence from bicycle seats, the
scientists said. What makes one person more vulnerable than another is
not known. Body weight seems to matter: heavier riders exert more
pressure on saddles. Variations in anatomy may also make a difference.
Dr.
Goldstein said he often saw patients who were stunned to learn that
riding a bicycle led to their impotence. One middle-aged man rode in a
special cycling event to honor a friend and has been impotent since. A
28-year-old who came in for testing, Dr Goldstein said, showed the
penile blood flow of a 60-year-old. A college student who had competed
in rough cycling sports was unable to achieve an erection until
microvascular surgery restored penile blood flow.
"We make kids wear helmets and knee pads," Dr. Goldstein said. "But no one thinks about protecting the crotch."