THE PHYSICIAN AND SPORTSMEDICINE - VOL 27 - NO. 5 - MAY 99
New Findings Reported on Biking and Impotence
In 1997, Irwin Goldstein, MD, a well-known impotence researcher and clinician from Boston University Medical Center, asserted that 100,000 men have suffered permanent impotence from bicycling (1). However, supporting scientific studies were lacking, and other urologists said his estimate was inflated.
New studies to be presented May 1 through 6 at the American Urological Association (AUA) meeting in Dallas bring the problem into sharper focus. They provide evidence that the problem does exist, give an idea of its prevalence, and show that female bicyclists aren't immune to perineal injury. (See "Bike-Related Perineal Problems: What About Women?" below.)
A Vulnerable Region
Concerns about riding-related impotence problems are not new, says Goldstein. "Hippocrates wrote that sexual problems were common among horsemen," he says. In the modern medical literature, case reports about biking and sexual dysfunction have appeared since the 1970s (2-4).
Goldstein says damage can occur when the bike seat—particularly the narrow racing type—focuses body weight on the pudendal nerves and artery, cavernosal artery, surrounding soft tissues, bony structures, and associated sexual organs. "The bike seat is archaic. It's unanatomic," he says. "The perineum is an intricate neurovascular complex, but there are no shoulder pads or helmets to protect it." Compression can lead to nerve damage, cavernosal artery insufficiency, and site-specific vaso-occlusion.
How Common a Problem?
Scientific evidence and estimates vary regarding the prevalence of impotence among bicyclists. Goldstein and his colleagues at Boston University, in a study (5) being presented at the AUA meeting, compared the rates of sexual and urinary dysfunction for 738 members of a bicycling club and 277 members of a running club who did not bicycle. Researchers found that the level of moderate-to-complete impotence in cyclists was significantly higher than in runners (4.21% vs 1.12%, p = 0.018). The only demographic difference between the groups was a higher rate of hypercholesterolemia among the bikers (10.6% vs 5.2%).
A 1997 cross-sectional study (6) of participants in a Norwegian long-distance bicycle race (540 km) found that of 260 men who answered the questionnaire, 22% (35) reported nerve symptoms such as numbness in the perineal area. Numbness lasted more than 1 week in 11 riders and more than 1 month in 3.
Roger Minkow, MD, an ergonomic product designer in Petaluma, California, who has designed a bicycle seat that reduces pressure on the perineal area (figure 1: not shown), says the Norwegian study presents an extreme situation. "Riders rode 350 miles in one position," he says.
Though the number of men who experience bike-associated numbness or impotence may not be as high as the Norwegian or Goldstein estimates, Minkow says the relationship between activity and injury is real. He estimates that 50% of men who ride a bike for 2 to 3 hours at a time experience perineal pain or numbness. "And sitting on a bike seat for more than 2 to 3 hours at a time can increase the risk of impotence," he says. Goldstein and Minkow both estimate that 4% of male bicyclists experience activity-related impotence. Goldstein says, "I've gotten hate mail (from biking enthusiasts) and have taken a lot of abuse for my claims, but 4% of 50 million bike riders is a lot of people."
How Big a Risk Factor?
Not all physicians agree that bicycle riding is a major risk factor for impotence. Harin Padma-Nathan, MD, director of The Male Clinic in Santa Monica, California, has said that the usual risk factors contribute to impotence in cyclists: diabetes, cigarette smoking, hypertension, and hypercholesterolemia (1). Also, he said most of the patients he's treated for bicycle-related erectile dysfunction have a history of a fall onto the top tube of a bicycle.
Goldstein agrees that a fall on a bicycle top tube can predispose patients to future impotence, but he insists that mounting evidence points to biking itself as a major risk factor. A study (7) being presented by Goldstein's group at the AUA meeting reports on a series of 81 patients who sought diagnostic evaluation for bicycle-related erectile dysfunction.
The men were relatively young (mean age, 41 + 11 years) and had few cardiovascular risk factors (a mean of 0.9 + 1). They rode an average of 88 miles per week, and 72% rode on narrow seats. Riding habits varied widely, including weekend riders, commuter bikers, stationary exercise bikers, teenage daredevil riders, avid road racers, and avid mountain bikers. Eight men (9%) recalled a bike accident that resulted in painful urination or hematuria.
Diagnosis and Treatment
Cycling-related perineal symptoms, which can be temporary or permanent, include numbness, pain, decreased orgasm sensitivity, and impotence. Numbness is a premorbid symptom, Goldstein says. "It can be a warning sign, but impotence can occur without it." The physical exam in patients who have symptoms doesn't provide much clinical information, he says.
Treatment involves rest from biking, and sildenafil is often effective for patients who are impotent, Goldstein says. For patients who have veno-occlusion, vascular reconstruction may reestablish potency, "but not everyone is a candidate."
Equipment changes can prevent recurrence. Switching to a recumbent bike can relieve pressure on the perineal structures, and patients should consider switching to a wider bike seat that allows the ischial tuberosities to bear more of the body weight. Also, there's a new bike seat on the market that is designed to take pressure off the perineal nerves and arteries (figure 1: not shown).
In an unpublished study, Minkow and Robert Kessler, MD, professor of urology at Stanford University Medical School, evaluated the efficacy of the seat among 25 bicyclists who responded to magazine and newspaper ads seeking bicyclists who had complaints of numbness, pain, or erectile dysfunction. The average age was 40.7 years (range, 27 to 68). Each rider was medically evaluated and given a questionnaire and the new bicycle seat.
After using the seat for 1 month, 14 riders responded that their symptoms were completely relieved, 10 reported improvement, and 1 reported no change. The authors concluded that the bike seat relieved symptoms, but noted that larger studies should be done to compare the effects of using a standard seat and the ergonomic seat.
Changes in riding practices, such as rising out of the seat every 10 minutes, may also help decrease the risk of bicycle-related impotence (table 1: not shown).
Goldstein places the responsibility for injury prevention on bicycle manufacturers. "The industry isn't addressing these problems, and I suggest two immediate changes," he says. "No child should be given a bicycle with a top tube, and seats should have no noses."
Bike-Related Perineal Problems: What About Women?
Bicycle-related perineal problems aren't just men's problems, according to researchers from Boston University. They have conducted a study (1) that they say is the first to document sexual and urinary tract dysfunction in female bicyclists.
The study, to be presented this month at the American Urological Association meeting in Dallas, included 282 female members of a bicycling club and 51 female members of a running club who served as controls. Ninety-eight percent of the bicyclists were road bikers; 11% were racers. Past injuries and symptoms among the bicyclists included traumatic contact with the bicycle top tube (32%), perineal numbness (34%), urethral stricture (1.8%), and pelvic fracture (1.5%). The mean ages of bicyclists and runners were similar (40 + 9 vs 42 + 12). No significant differences were found in the rates of cardiovascular risk factors, education, race, or frequency of sexual intercourse.
The researchers say that similarity between men's and women's bike-related injuries from compression or trauma isn't surprising because certain parts of the male and female sexual anatomy are similar—specifically, the orientation and course of the pudendal neurovascular bundle within Alcock's canal and medial to the ischiopubic ramus.
Kidney Disorder Linked to Creatine Use?
In a reply published in the same issue, a spokesman for the creatine manufacturer (General Nutrition Products, Greenville, South Carolina), noted that the product label warns users not to take the loading dose of 20 g per day for more than 4 days in any 1-month period. The spokesman, Ronald W. Thompson, PhD, said controlled studies of creatine's effect on performance—none of which involved taking 20 g/day for 30 days—have revealed no major side effects.
Evading Lightning at Sports Events
Mountain Bikers' Injury Lingo
Auger: to involuntarily take samples of the local geology, usually with one's face; also called "soil sample" or "face plant"
Bacon: scabs on a rider's knees, elbows, or other body parts
Beartrap: to slip off a pedal, causing it to slam into the shin; toothlike scars resulting from being beartrapped
Chainring tattoo: the dotted-line scar obtained from gouging one's shin on the chainring
Cranial disharmony: how one's head feels after "augering"
Endo: the maneuver of flying unexpectedly over the handlebars, thus being forcibly ejected from the bike; short for "end over end"
Hamburger: the condition of skin, post "auger," when geological contact was made with sharp rocks
Involuntary dismount: a crash
Mandibular disharmony: how one's jaw feels when it and the handle bars attempt to occupy the same space and time
Over-the-bar blood donor: a rider who is injured while doing an "endo"
Stoned: describes a rider after a crash that embeds stones in the rider's skin.
A Growth Hormone Test for the 2000 Olympics?
In a related development, a letter in the March issue of The Lancet details a new detection method developed by German and Danish researchers. The researchers tested routine laboratory samples and those taken from patients undergoing treatment for adult growth-hormone deficiency. They correctly identified all of the samples from patients who had received synthetic growth hormone.
In-Line Skating Week Includes Lessons, Events
As an injury-prevention tool for use any time of the year, physicians can encourage patients to seek proper instruction in the sport. The IISA Web site has a searchable list of certified skating instructors. Also available online or by mail is a safety guide for novices.
The IISA Web site reports a little-known fact about in-line skating: The activity has spawned a third competitive sport (alongside in-line skate racing and hockey)—in-line basketball.