Photo: JamieL.WilliamsPhotography/Flickr

Elite bikers are true endurance superstars. Ironman athletes stay in the saddle for 112 miles. Amazing. But it's a mere drop in the hat when you consider the Tour de France goes for over 2,000 miles (over approximately 23 days). All of the hours spent training and racing may give male competitors some of the most awesome legs around -- but they don't do the bikers any favors in the fertility department.

According to recent research, sperm quality drops with vigorous biking. Running and swimming don't have a negative impact on sperm quality. But multiple biking factors can cause the littlest swimmers to get a bit shy. Why? Researchers explain that the heat from tight clothing, friction against the bike's saddle and sheer stress on the body from vigorous activity contribute to the reduced sperm quality.

Now for the good news: The most severe fertility issues were seen in athletes who were logging more than 186 miles per week on their bikes. So biking a few days a week for exercise or commuting to work on your bike isn't likely to affect fertility.

The biking and infertility link is simply a case of "too much of a good thing." And it's a reminder to all of us that you should shake up your workout from time to time. Adding variety to your workout is good for many reasons -- it keeps things interesting, and it presents ever-changing challenges for your body. Even when training for a distance race, it's a good idea to incorporate complementary activities into your your training routine.