Extreme mountain biking linked to lower sperm count

OB/GYN News,  Feb 1, 2003  by Patrice G.W. Norton

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CHICAGO -- Compared with noncyclists, roughly 90% of mountain bikers who logged 3,000 miles or more a year had lower sperm count, decreased sperm motility, and scrotal abnormalities, Dr. Ferdinand Frauscher said at the annual meeting of the Radiological Society of North America.

To prevent possible loss of fertility, male mountain bikers should invest in bicycles with shock absorbers and better suspension features, which could double the cost of a mountain bike but potentially protect bodily functions influencing fertility, said Dr. Frauscher, head of the department of uroradiology at University Hospital, Innsbruck, Austria.

He reported on a study that compared 35 noncyclists with 40 extreme mountain bikers, who rode more than 2 hours a day, 6 days a week for more than 3,000 miles a year. Ages ranged from 18 to 44 years for the extreme cyclists and 17 to 41 for the noncyclists.

Ultrasonography, using a 12-MHz transducer, showed scrotal abnormalities in 35 bikers (88%) and 9 nonbikers (26%).

Abnormalities in the biking group included 25 scrotal calculi, 22 epididymal cysts, 14 epididymal calcifications, 13 testicular calcifications, 6 varicoceles, 5 hydroceles, and 3 testicular microlithiases. In noncyclists there were six epididymal cysts, two testicular calcifications, and three varicoceles. A total of 21 bikers (52%) reported a history of intermittent scrotal pain, compared with 7 noncyclists (20%).

Similar findings were reported in a 1999 study by Dr. Frauscher. In this study of a new group of subjects, he and his associates also measured semen volume, sperm count, and sperm motility.

On average, extreme mountain bikers had one-third the sperm count that noncyclists had, and had a significant decrease in semen volume per ejaculation (2.7 mL in bikers vs. 4.0 mL in nonbikers). The fraction of motile sperm was 29% in mountain bikers and 52% in noncyclists.

A significant correlation was found between sonographic abnormalities and changes in semen volume and sperm motility in extreme mountain bikers, but not so in noncyclists. The study identified no significant hormonal differences between the two groups.

The exact causes for the decreased sperm motility are unclear, but Dr. Frauscher theorized that repeated mechanical trauma to the testicles results in some degree of vascular damage, which may lead to a reduction in sperm motility. Higher altitudes did not appear to account for the results, and other factors such as alcohol and smoking were hard to pin down. Some of the conditions identified in the study are treatable, but mountain riders may want to look closely at the finding that 63% of bikers had scrotal calcifications. "I've never seen calcification of organs reversible," Dr. Frauscher said. The researchers did not look for prostatitis in the bikers, but he suspects it would be higher, as it is in rodeo riders.

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