Groin Numbness and Bike Riding
Bike riding is terrific aerobic exercise, a healthy and economical way to commute, and a great way to run errands, sightsee, and get around town. There is, however, a potential downside to biking; sitting on the bicycle seat may result in the compression of nerves and blood vessels of the vulnerable area of the body called the perineum. The perineum is the area between the anus and the base of the penis in males and between the anus and the vagina in females; it contains both blood vessels and nerves. Compression of the perineum can lead to nerve damage, swelling, artery insufficiency (lack of blood flow through the vessel), and even occlusion (blockage) of blood vessels, which in turn can lead to temporary or permanent groin numbness, tingling sensations, decreased penile blood supply, erectile dysfunction (impotence), decreased orgasm sensitivity, and pain. These cycling-related perineal symptoms are the subject of this article.
How common are cycling-related perineal symptoms?
Perineal symptoms are not experienced by all cyclists, but this is certainly something to be aware of, particularly if you plan to ride long distances.
What are factors that cause perineal symptoms?
Vertical loads of the perineum to the saddle can be as high as 52% of the rider's body weight, whereas shear loads can reach 12% of body weight. The vertical pressure is dependent on the rider's body weight as well as riding position. Although there is no conclusive data as to what degree of load increases the likelihood of symptoms, there does appear to be a relationship between load stress and compression of the perineum.
Saddle and handlebar height
In a study of erectile dysfunction and bicycle characteristics, researchers determined that keeping handlebar height lower than saddle height in long-distance cyclists was associated with less erectile dysfunction, perhaps because this configuration puts the rider in a leaning-forward position which may reduce vertical load on the perineum. This position may or may not apply to recreational riders on touring or hybrid bikes where speed and aerodynamics are not as important, but there is no research to support the claim one way or the other.
In three studies of the angle of the saddle, it was confirmed that a downward tilted saddle reduced stress and compression on the perineum. This is probably because the backward stress puts the weight of the rider on the ischial tuberosities (the "sit bones" in your buttocks) and off of the perineal cavity.
Bicycle saddle design has been the target of a great deal of scholarly and commercial research. A number of years ago, bicycle saddles started to be manufactured with cutouts down the middle with the hope that this would relieve pressure on the perineum and reduce compression symptoms. Indeed, in one study, 55% of the subjects ranked the partial cutout saddle as the most comfortable. In a recent study of a new saddle (Selle SMP) with a large cutout and downward facing nose (the front of the saddle), the saddle was clearly superior in preventing vascular compression and penile blood flow occlusion compared with more standard saddle designs.