The Association of Bicycle Related Genital Numbness and Sexual Health Inventory for Men Score (SHIM): Results from a Large, Multinational, Cross-sectional Study - Beyond the Abstract

In the 1980s, there were multiple reports of male cyclists developing a constellation of symptoms after long distance bicycle rides including perineal/genital numbness and erectile dysfunction.1,2  A larger study of men engaging in a long distance cycling event (330 miles) demonstrated 21% of men experience persistent numbness and 13% of men experience erectile dysfunction.3  Although these symptoms were observed in cyclists engaging in events with prolonged time in the saddle, the relationship between cycling and erectile dysfunction received a substantial amount of attention and press leading to concerns for increased rates of erectile dysfunction in recreational cyclists.4  More recently, a large study of 3932 men from our group demonstrated no increase in incidence of erectile dysfunction among cyclists compared with runners and swimmers.5  However, there remain a small group of cyclists who ride for long distances that remain at risk for development of genitourinary maladies due to the prolonged exposure to a seated position on a narrow firm bicycle saddle while traveling over irregular surfaces.

Multiple studies have demonstrated a decrease in blood flow to the penis while sitting on the saddle as a potential mechanism for erectile dysfunction in cyclists.6,7 However, palsy of the perineal nerves due to microtrauma has also been a purported mechanism that explains both the genital numbness as well as erectile dysfunction seen in cyclists.8,9 In this study, we sought to quantify the absolute increase in pressure related to road or terrain irregularities. We performed this study in a controlled laboratory setting with a mechanism to simulate going over various sizes of bumps. We measured the changes in pressure during this process at a rate of 100 measurements per second. We found that even when going over small bumps, there is a 10% increase in pressure compared with baseline, which increases to 19% with going over slightly larger bumps.  Furthermore, the increases in overall pressure appear to be concentrated in very specific areas of the perineum, which were different in men and women. Using a very simple spring-loaded seat post shock absorber, we were able to demonstrate a 50% reduction in the pressure associated with the bumps in a stationary/coasting position.  

It should be noted that the bumps used in this study represent a relatively small amount of oscillation compared with riding at 10-20 mph over real road conditions encountered by cyclists. Thus, we believe that for those cyclists engaging in cycling events with prolonged time in the saddle, there may be a role for shock absorption in relieving the numbness and erectile dysfunction seen in this population. Furthermore, it may simply help cycling be less of a pain in the butt.  

Written by: Thomas Sanford, MD, National Institutes of Health 

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