Depending on which study you read, cycling will either improve your health or leave you impotent and sterile. It’s hard to get a grasp on what exactly cycling does to a man’s privates, and chances are, you’re tired of wondering whether you’re sacrificing your family lineage every time you go for a spin. So we’ve analyzed the various cycling-infertility studies and come up with a practical primer that gives you the bare bones about what riding actually does to your nether regions.

In 1997, a Boston University study linked standard bike seats to impotence, citing the consistent pressure on certain key arteries. At the time, Dr. Goldstein, the doctor in charge of the study, claimed that cycling directly caused male impotence. Many reproductive specialists said Goldstein’s study was too small to provide conclusive proof and that Goldstein was overstating the link between impotence and cycling. Several years later, Goldstein has softened his position and admits he may have been overconfident.

Recently, the male genitalia buzz is focused on mountain biking. And this time, it’s not impotence, it’s infertility. In 2002, a study by Dr. Ferdinand Frauscher, an Austrian urology-radiology specialist, provided mind-boggling statistics about mountain bikers. Ninety percent of the mountain bikers Frauscher studied had low sperm counts, scrotal abnormalities, and decreased sperm motility, compared to only 26 percent of the non-cyclists involved in the study.

“We believe that extreme mountain biking results in semen alteration, which may have an impact on fertility,” Dr. Frauscher said at an annual meeting of the Radiological Society of North America in 2002. “Repeated mechanical trauma to the testicles results in some degree of vascular damage, and may thereby cause a reduction in sperm motility.”

Lower sperm count and decreased sperm motility reduce the ability to conceive, which could mean there will be far fewer mountain bike tykes in the world. But don’t panic. The bikers in the study logged more than 3,000 miles a year on a mountain bike. You’d have to ride more than eight miles a day, every day, for a year to log that kind of distance. Plus, it was a really small study. Only 55 mountain bikers participated, which leaves many fertility specialists questioning Dr. Frauscher’s findings.

However, there is a good chance excessive biking does some sort of damage to your luggage, so we figure it’s better to be safe than sorry. Short of quitting cycling altogether, there are a couple of things you can do to protect the family jewels.

First, make sure your bike seat has a long narrow canal in the middle. Most bike manufacturers now offer this “impotence-free” seat that relieves compression on the critical arteries.

The seat will keep the air in your sail, but it won’t do a thing for infertility, which is caused by trauma, not arterial compression. If children are in your future, you might want to fork over the extra cash for a full suspension bike. Dr. Frauscher says tail-end suspension bikes will reduce the amount of trauma to your sensitive area. And most full suspension bikes now come standard with impotence-free seats, which all but guarantees that your next mountain bike ride will be an uplifting experience.

-Graham Averill