How Bicycling Affects Male Fertility

Men may want to hang up the (bike) saddle while trying to conceive

Cyclist on the road | CU Advanced Reproductive Medicine

Surprisingly little data are available on whether bicycling, particularly at moderate levels, has any impact on fertility. Many of the studies available are small and involved elite level athletes. There is relatively little data available regarding bicyclists who may be competitive but not at the elite or professional level, and there is even less data about the “weekend warrior” who may only go bicycling two to three times per week. Still, that covers a lot of cyclists in Colorado.

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Representing the type of study involving elite athletes, a group from South Africa looked at 10 long-distance competitive cyclists and 10 sedentary controls. The only difference found between the groups was that the bicycling subjects had a much lower percent of normal morphology (appearance of the sperm) when compared with the sedentary men.

A more pertinent study for weekend cyclists is a 10-year survey by a Boston-area fertility center that observed 2,261 men—from all walks of life and not just elite athletes—who contributed over 4,500 samples of sperm. Investigators correlated the sperm parameters with the level of exercise, focusing on sperm density (the number of sperm per milliliter), sperm motility (the percentage of sperm that were moving), and sperm morphology (what the sperm look like).

The study found that men bicycling more than five hours per week had a lower sperm concentration than either sedentary men or those doing other types of exercise. It’s also interesting that the association with the lower sperm counts was not affected by the patient’s age or weight.

It is important to point out that, while differences are found in these sperm parameters, no study has clearly shown that there’s a difference in terms of the most important outcome: fertility. Indeed, this sort of study would be very difficult to conduct.

Shift your cycling style

What causes the lower sperm parameters in bicycling males? Several theories have emerged but none is conclusive.

  • Working out in general may cause hormonal factors such as testosterone to decrease and cause lower sperm production at the level of the testis. Yet evidence suggests that bicycling is the only exercise that has an impact on sperm production.
  • It is well established that long-distance bicyclists support a significant percentage of  weight on the perineal body area between the testis and the rectum. This trauma can affect blood flow to the testis, which can also negatively impact the production of sperm.
  • Local impact on the testicular and perineal area may impact sexual function. Studies show significant nerve or vascular injury in some individuals who bicycle intensely or for long periods. Genital numbing may persist in some men for a long time, which can significantly affect sexual function. Bicyclists also report erectile dysfunction.

While discouraging bicycling may seem to be a reasonable approach in men who are trying to achieve a pregnancy, they can modify the way they bike by finding appropriate saddle height, saddle shape, and handlebar height, all of which can impact the amount of pressure placed on the genital area. Increasing the width of the back part of the seat, which supports the bony prominences of the pelvis, may help to take some of the pressure off of the genital area.

If this does not seem to help the sperm parameters, the male should consider temporarily discontinuing bicycling while the couple is trying to achieve a pregnancy. Sperm take approximately 70 days to develop from premature to mature forms. Allowing sperm parameters to return to normal during this extended period of time may be of benefit, particularly in individuals who have an abnormal semen analysis. Once a pregnancy occurs, the male partner can return to biking his usual distance and intensity.