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Serious Cycling May Affect Male Fertility, Says Study

Image of cycling and male fertility

by Leigh Ann Woodruff, May 24, 2012

Men, if you're a serious cyclist, you may want to downgrade your level of participation to recreational if you and your partner are trying to get pregnant. A new study out of the UCLA School of Nursing found that serious leisure male cyclists may experience hormonal imbalances that could affect their reproductive health.

"Although preliminary, these findings warrant further investigation to determine if specific types of exercise may be associated with altered sex hormone levels in men that could affect general health and reproductive well-being," says Leah Fitzgerald, Ph.D., FNP-BC, assistant professor at the School of Nursing and senior author of the study, which was published in the European Journal of Applied Physiology.

While many have theorized that cycling can affect male fertility because increased scrotal temperature can reduce sperm production, researchers at UCLA investigated the association between exercise intensity and circulating levels of the reproductive hormones, such estrogen and testosterone, in serious leisure male athletes (triathletes and cyclists) and recreational athletes. There were 107 healthy male athletes, ages 18 to 60, who participated and filled out the International Physical Assessment Questionnaire to obtain an objective estimate of time spent participating in different levels of physical activity and inactivity during the previous seven days. The researchers divided the participants into three groups — 1) triathletes, 2) cyclists and 3) recreational athletes.

The athletes had blood tests to measure total testosterone, estradiol (estrogen), cortisol, interleukin-6 and other hormones.The researchers found that estradiol and testosterone levels were significantly elevated in male cyclists. Estrogen levels were more than two times higher in the cyclists than the triathlete or the recreational athlete, and total testosterone levels were about 50 percent higher.

In males, estradiol is produced as an active metabolic product of testosterone. A condition associated with elevated estrogen in males includes gynecomastia, a condition that may result in the loss of male pubic hair and enlarged breast tissue. The study also found an association between an increase in estrogen levels and increasing years of chamois cream use. Cyclists apply chamois cream — which may contain parabens (anti-microbial preservatives and weak estrogen agonists) to their perineum area to help prevent chaffing and bacterial infections related to bicycle saddle sores.

However, bike enthusiasts should not panic, according to Eric Widra, M.D., a fertility doctor with Shady Grove Fertility in Washington, D.C. "Nothing in this study shows that these men had decreased fertility or sperm production," he says. "According to the text, it doesn't even look like they checked a sperm count. It is normal for men to have some circulating estrogen. 'Twice as high' is probably still too low to be meaningful."

Dr. Widra explains that In severley obese men who have infertility and low sperm counts, there is some evidence that very high estrogen levels produced by the fat cells may play a role in infertility.

So, should men put away the bikes if trying to conceive? "Unless they are having fertility issues AND have an abnormal semen analysis, I would not recommend any changes," Dr. Widra says. "There is a stronger link between cycling and sexual dysfunction. If this is occurring, he should consider changing to a different seat and consulting with a urologist with expertise in this area."


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