Feb 5, 2013 6:13 PM
Feb. 5, 2013 -- Healthy young men who watch TV for more than 20 hours a week have almost half the sperm count of men who watch very little television. But men who do 15 or more hours of moderate to vigorous exercise every week have sperm counts that are 73% higher than those who exercise for less than five hours a week, according to a new study published in the British Journal of Sports Medicine.
Allan Pacey, PhD, British Fertility Society chairman and senior lecturer in andrology at the University of Sheffield, says the findings fit with what fertility experts already know.
"We know that men who wear too tight underwear have poorer sperm. So it's not a million miles away from sitting on the sofa ... for too long and heating up your testicles for too long. It's the same mechanism I would suspect."
And the findings about helping sperm quality with exercise also fit. "Men who are out on the golf course are not only getting cardiovascular benefits from doing even light exercise, but there are also some metabolic benefits as well."
Semen quality appears to have deteriorated in most Western countries over the past few decades for reasons that are not clear. The study authors set out to find if an increasingly inactive lifestyle might play a role.
They analyzed the semen quality of 189 American men, all from New York state, between the ages of 18 to 22 in 2009-10.
The men were asked about the quantity and intensity of weekly exercise over the preceding three months and how much time they spent watching television, DVDs, or videos over the same period.
The men were asked to say how many hours they usually spent a week doing vigorous, moderate, or mild exercise. They also said how much TV they watched on an average day, from none or almost none at all to over 10 hours.
Men who were more physically active tended to have a healthier diet than those who watched a lot of TV every week.
The analysis showed that those who were the most physically active -- 15 or more hours a week -- had a 73% higher sperm count than the least physically active.
When analyzed by exercise intensity, the results showed that light physical exercise made no difference to the sperm count, no matter how frequent it was.
TV viewing had the opposite effect. Those who watched the most -- 20 or more hours a week -- had a sperm count that was 44% lower than those who watched the least.
Unlike smoking or weight, the amount of TV viewing seemed to counteract the beneficial effects of exercise, although this may be a chance finding, the authors say.
The authors caution that a reduced sperm count does not necessarily curb a man's fertility or his chances of being able to father a child. But the findings do suggest that a more physically active lifestyle may improve semen quality.
The type of exercise might also be important, they say. "Future studies should also evaluate the extent to which different exercise types affect semen quality."