Erectile Dysfunction and Bicycling
by Irwin Goldstein, MD
Erectile dysfunction (ED) is a common condition that has affected men for centuries. Although ED was once considered a benign complaint, we now recognize that ED and sexual health have a profound impact on the overall health and quality of life of affected men and their partners. Epidemiologic studies show that the risk of ED increases with advancing age and that the typical patient with ED is generally in his 50s or 60s. There is increasing evidence, however, that ED also occurs in much younger men. ED may be caused by psychological factors or hormonal problems as well as by chronic disease or acute injury. Recently, there has been growing interest in the role of bicycling in the development of ED, particularly in young, otherwise healthy men who lack the typical risk factors, such as hypertension, elevated lipids, and cigarette smoking.
In addition to being an economical and efficient form of transportation, bicycling has become a popular activity for relaxation, exercise, and weight loss. The aerobic exercise required for biking has strong cardiovascular benefits and has also been shown to reduce the risk of diabetes and hypertension. As for the Scythians, however, who identified horseback riding as a possible cause of male impotence in the ninth century BCE, the relationship between bicycle riding and ED has become a matter of concern. Numerous case reports have been published of bicyclists with erectile difficulties and/or perineal nerve dysfunction that resolves with changes in cycling techniques, rest, or use of a softer saddle. Small observational studies have also showed a relatively high prevalence of ED among elite cyclists, who often report penile numbness and changes in sensation after cycling. These effects have been confirmed in pathophysiologic studies that describe compression-related changes in perineal structures, as well as in studies of stationary bicycling, which show a significant decrease in penile blood flow during seated biking and a return to above normal when the rider stands.
Although this research all points to a relationship between ED and bicycling, this association has been demonstrated only recently in a population-based random sample of men. Researchers evaluated data from the landmark Massachusetts Male Aging Study (MMAS), a large cross-sectional survey of 1709 free-living men in their 40s to 70s. The random sample is representative of a similar population of men and includes a variety of cyclists, such as recreational and occasional riders, stationary bikers, and serious sport cyclists. This is unique among studies done on ED and bicycling to date, and it allows the findings to be generalized to the entire population of cyclists.
Bicycling and the Male Anatomy
Before we discuss the findings of the MMAS, a brief anatomy review should help explain how bicycling can contribute to or cause sexual dysfunction. When humans sit, they bear their weight on the ischial tuberosities, or what we have come to refer to as the “sit bones.” The ischial tuberosities have no organs attached to them and no nerves or arteries; they are surrounded by the fat and muscle of the buttocks. This area is very well vascularized and allows humans to sit comfortably and safely for hours.
Unfortunately, most bicyclists bear their body weight on a bicycle seat that is not wide enough to support the ischial tuberosities. As a result, they wind up straddling the bike and, in effect, sitting on the internal part of their genitals. The penis (and the female clitoris) is attached deep within the pelvis. It does not end, as it appears to, at the scrotum but rather near the anus. Like the roots of a tree, this internal part of the penis provides stability so that an erection doesn’t buckle as the penis penetrates the vagina.
The Straddle Position and ED
In the straddle position, body weight is supported not by the ischial tuberosities but by the ischiopubic rami, the connector bones that join the ischial tuberosities to the pubic bones. Unlike the ischial tuberosity, which has evolved into the perfect place to bear body weight, the ischiopubic ramus is a working area that contains erectile tissue, nerves, arteries, and the urethra. As a result, the bicycle rider bears his weight directly on an area where the nerves and arteries enter the penis. This area is a tubelike structure called the Alcock canal, which lies along the ischiopubic ramus. Straddling compresses the nerves and arteries running through the Alcock canal against the ischiopubic ramus, which frequently results in complaints of numbness in the penile/scrotal area after cycling. Importantly, straddling may also lead to localized atherosclerosis and compromised blood supply to the penis, resulting in ED.
Traditional atherosclerosis is initiated by endothelial injury, which triggers a series of events that result in inflammation, plaque formation, calcification, and eventual blockage of the artery. Endothelial injury generally occurs in individuals with risk factors such as elevated lipid levels, cigarette smoking, diabetes, or hypertension. Substantial evidence exists that localized blunt trauma to the penile artery can also injure the endothelium. What occurs in a healthy 22-year-old bicycle rider, however, differs from what takes place in a 62-year-old in that the older man will most likely also have atherosclerosis of the coronary, cerebral, and leg arteries in addition to the penile arteries. His ED occurs as part of a systemic vasculopathy. In contrast, although the 22-year-old has atherosclerosis of the penile artery, his cerebral, coronary, and leg arteries are perfectly healthy. The blunt trauma to the endothelium caused by straddling is believed to be the inciting factor for this man’s localized atherosclerosis.
Two kinds of injury can actually lead to atherosclerosis in a bicyclist. The first is a chronic compressive injury, which is what occurs among sport cyclists who ride hundreds of miles a day. The other and perhaps more obvious cause of endothelial injury is not chronic compression but an acute crushing injury. A good example of this is a young boy who tries to ride his older brother’s bicycle, only to slip and fall on the bar and land on the Alcock canal. A similar injury can also occur in an older boy who falls on the horn of a narrow saddle. Here again, the penile artery gets crushed and the endothelium is injured, initiating the atherosclerotic process that results in ED.
The Risks and Benefits of Bicycle Riding
Despite the potential risks posed by bicycling, this popular form of exercise provides huge benefits. Approximately 131 million Americans bicycle because it is an inexpensive, uncomplicated, and easy-to-learn activity. Bicycling can be learned at an early age and is accessible to people of all ages; it can be done year-round, indoors or outside. Unfortunately, only about 15% of adult Americans engage in regular physical activity (ie, 20 minutes of activity 3 times a week). Sedentary individuals have a 30% to 50% greater risk of developing hypertension, which in turn is associated with chronic heart disease and ED. In contrast, regular exercise improves cardiovascular health, lowers blood pressure, improves lipid levels, and lowers the risk of ED.
A key finding of the MMAS was the relationship between moderate cycling (<3 hours per week) or sport cycling (>=3 hours per week) and the development of ED. The 3-hour period was selected because it reflects a typical amount of exposure for stationary riders going to a gym as well as for commuters who ride about 15 minutes each way to work every day. Analysis of the data showed that individuals who cycle at least 3 hours per week have an odds ratio for developing moderate or complete ED of 1.72. (Odds ratios >1.5 are defined as health risks.) That is, at least 3 hours of cycling per week was more likely to caused artery blockage and long-term damage. More significant, however, was the finding that men who bicycle less than 3 hours per week or who ride only occasionally have an odds ratio of 0.61 for developing moderate or complete ED. This indicates that moderate exercise in the form of bicycling can, in fact, prevent ED.
As noted earlier, studies have shown that a sedentary lifestyle increases the risk of heart disease and the probability of developing ED. In the MMAS, men who remained physically inactive had the highest risk for ED, whereas those who began exercising or who continued to exercise throughout the study had the lowest levels of ED. This new MMAS analysis further confirms the value of exercise, particularly bicycling. Moderate cyclists were found to be less likely to have moderate or complete ED than men who do not cycle, whereas sport cyclists were more likely to have moderate or complete ED. There was also some suggestion that substituting bicycling for another activity may even protect against ED.
Ultimately, men must make their own decisions about the risks and benefits of bicycle riding. As this recent MMAS analysis has demonstrated, most men can take advantage of the many benefits of moderate bicycle riding without worrying that it will lead to ED. Before they begin to ride, however, they should be aware of the need for a properly fitting bicycle and comfortable saddle as well as the potential risks to sexual health presented by long-distance cycling. Finally, supervising children and providing them with properly fitting bicycles and seats—just as we do with protective helmets—is also essential to avoid injury and preserve sexual functioning.
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