Guys, it may be time to get off the couch and hit the treadmill — especially if you want to have kids.
Okay, we all know that exercise is good for us. It can reduce the risk of obesity, diabetes and heart disease, to name a few benefits. Now researchers say physical activity may also help keep sperm healthy and happy.
A study published Monday in the British Journal of Sports Medicine suggests that how physically active a guy is can affect his total sperm count and sperm concentration.
Researchers surveyed 189 young men (ages 18 to 22) on their exercise and TV-watching habits over a three-month period. They also collected and analyzed the participants' semen.
Men who watched 20 or more hours of TV per week had a sperm concentration 44 percent lower than those who watched almost no TV. On the other hand, men who exercised more than 14 hours per week had a sperm concentration 73 percent higher than men who exercised less than five hours per week.
These effects held true even when other factors like body weight, stress and diet were taken into account.
According to lead author Audrey Gaskins, a doctoral student at Harvard School of Public Health, sperm concentration and total sperm count are two of the main factors that clinicians consider in assessing male fertility.
So is being active the key to fertility?
Not so fast. Gaskins cautions that it's not possible to make conclusions about cause and effect in a study like this one. "Ideally, we would have done a randomized control trial where we had men switch from different behaviors and then measured the results," she says.
She also points out that different types of physical activity may have different effects on semen quality. For example, both biking and long-distance running can actually reduce semen quality, according to previous studies.
Nevertheless, this study might be onto something. A year ago, while conducting separate research on how diet affects semen quality, Gaskins and her team noticed that physical activity kept showing up as a significant factor. "It caught our eye," she says. "That's when we decided to look into it further."
It's unclear why physical activity might affect sperm count. Gaskins hypothesizes that it's because exercise protects against oxidative stress, which can damage male germ cells. You lose that protection when you sit around all day in front of the TV.
Sperm production is sensitive to temperature. So being a couch potato may thwart sperm production by increasing scrotal temperature.
Are the ill effects of a sedentary lifestyle on sperm permanent? Gaskins says more research needs to be done to answer that question. However, because it takes about three months to produce new sperm, couch potatoes probably aren't doomed to suboptimal semen. "That's the nice thing about male fertility," she says. "It seems to be more potentially modifiable."