A research report out of Harvard this week and published in the British Journal of Sports Medicine indicates that men who are sedentary and watch around 20 hours of television had decreases in sperm counts.

In the study, 189 men, who were students at a university in New York, were asked to record how many hours in a typical week they had spent watching TV or doing physical activity. Additionally, each volunteer was asked to provide a sperm sample for analysis.

When the comparison between active lifestyle and sperm count was made, researchers found a link between the two, showing that not being active resulted in a lower sperm count.

The results of the study showed that those who were active and spent 15 or more hours of their week exercising, by playing sports, for example, had a sperm count that was 73% higher than those who were the least active.

Men who spent a lot of time in front of the TV, for at least 20 hours a week, had a sperm count that was 44% lower than men that had not spent much time in front of the television.  No participant had sperm counts that would qualify them as infertile or sub-fertile.  Other features of participants sperm, such as how well they are able to swim or their shape, two features that can also affect fertility, were not affected. 

Researchers didn't pinpoint the reason behind the disparity and didn't break down the sperm quality based on sports played.  It is known that temperature affects sperm production and that cool conditions are optimal for proper sperm production and health. It may be possible that sitting for extended periods of time may increase scrotum temperatures and negatively affect sperm production.

Sperm counts in the developed world have been dropping steadily for the past few decades.