From fixed-gear aficionados to daily commuters to recreational users of bicycle-sharing services like Lime Bikes and Ford GoBikes, travel anywhere in the San Francisco Bay Area and you may see evidence of the cycling culture our region has to offer. San Francisco has earned its reputation as one of the most “bike friendly” cities in the nation.
Bicycling.com named San Francisco as its #2 “Best Bike City” in the United States in its latest biennial review. Meanwhile, cycling has no doubt also helped to secure San Francisco, including the East Bay, the sixth spot on Forbes 2016 “Healthiest Cities” list.
While the physical and mental health benefits of cycling are clear, there can be negative urological consequences too. As urologists, we believe a consistent focus on cycling style and bike setup will help mitigate any undesirable consequences and keep you in the saddle all season long.
The most common adverse conditions that have been reported to be associated with cycling are nerve entrapment leading to genital numbness, as well as vascular injury leading to erectile dysfunction. These phenomena are usually found in men who cycle intensively or for long periods at a time – sports cycling rather than recreational cycling.
A recent large multinational study showed that there was a significant increase in genital numbness with years of cycling, more frequent weekly cycling and longer cycling distance per ride. This is thought to be due to entrapment of the pudendal nerve between the pelvic bones and the nose of a bicycle saddle. However, researchers also found that there was no significant difference in erectile dysfunction between those with and without genital numbness.
Another multinational study of 5,488 male athletes compared cyclists to swimmers and runners and found that cyclers had no worse sexual or urinary function but were more prone to urethral strictures, a condition where scar tissue accumulates within the urethra.
Women can also experience negative impacts of cycling consistent with pressures on the perineum. It has been reported that certain saddle designs and handlebars set lower than the seat can also lead to pain and numbness for women, swelling of the labia, possibly leading to increased sexual dysfunction. Furthermore, a large cross-sectional study of women cyclists found that they were more likely to report genital numbness, saddle sores and urinary tract infections compared to noncyclists.
Cycling may also have a negative effect on male fertility. One study found that of 2,261 men being evaluated at Boston-area infertility clinics over a 10 year period, men who reported bicycling more than five hours per week had a lower sperm concentration than either sedentary men or those doing other types of exercise. Physical activity may be generally beneficial for fertility, as another study found that while men who engaged in moderate-to-vigorous exercise weekly had higher sperm concentrations compared with their sedentary counterparts. However, in that same study, men who reported cycling just more than 1.5 hours weekly had lower sperm concentrations compared with men who reported no bicycling.
It has been long known that increased temperatures from saunas, hot tubs, and even tight-fitting underwear and clothing can affect semen parameters and in turn fertility. Studies have even been done on the effect of bicycling on scrotal temperature. This temperature change may explain how long term, intensive cycling can lead to lower semen volume, motility, morphology and concentration, possibly through increased levels of reactive oxidative species and cytokines that affect sperm production and maturation. However, it is still unclear whether these changes in sperm quality are associated with decreased pregnancy rates.
How you can improve cycling safety
- Not all seats are created equal. According to one study, “no-nose” saddles have been shown to decrease pressure in the front of the pelvic area and perineum for men, and increase blood flow to the penis when compared with traditional and cut out saddles. Another study found that, while traditional saddles exert less pressure on the perineum, a wider saddle with decreased perineal pressures and overall total saddle pressures may be better for women.
- Position and height. While there are many benefits to riding with handlebars lower than the saddle position (both aerodynamic and shortened bike geometry are preferred by road cyclists), several studies have down that raising the handlebars above the saddle greatly decreased pressures on the perineum and genital area, thereby decreasing genital numbness. Proper seat height can greatly reduce chaffing and unnecessary pressure on the rider. A general rule of thumb: when placing your heel squarely on the pedal at its lowest point, your leg should be fully extended with your hips remaining in a horizontal position.
- Riding style. Take breaks from riding when the genital area becomes numb or hurts. When it is not possible to stop, try riding out of the saddle for a minute or two to relieve pressure in the genital area and restore blood flow. One study showed that standing more than 20 percent of the time while cycling reduces the risk of genital numbness.
- Regarding male factor infertility, men experiencing low sperm counts should consider temporarily discontinuing bicycling while trying to achieve pregnancy. Sperm take approximately 70 days to develop from premature to mature forms.