2,200 men participated in the survey study. They each provided a semen sample and reported on their daily health and exercise status. After controlling for nutritional levels, weight, blood pressure, underwear style and other factors, the researchers concluded that men who cycled for more than five hours per week had lower sperm counts and sperm motility than other men.
The data showed that 23% of men who lacked exercise had low sperm counts; this number rose to 31% among men who cycled more than five hours a week . In addition, 40% of “cycling men” have insufficient sperm motility, which is also higher than that of inactive men.
Injury to the scrotum or warming of the scrotum may explain the link between cycling and lower sperm health, said Laura Wise, an associate professor at Boston University who led the study.
The study also showed that men who exercised regularly and who exercised at a high intensity were less likely to have problems with sperm count and motility than men who exercised less.
Wise, explaining the purpose of the study to Reuters, said that previous studies in competitive athletes have shown that cycling has an effect on the urinary system and semen quality, “but in men who exercise regularly, we’re not sure we can find that association.”
However, Wise acknowledged that the survey results may not be generalizable because the men surveyed were all from male clinics, and the final results still need to be verified by more research.