Men who watch more than 20 hours of TV a week have almost half the sperm count of those who watch hardly any, according to a study.
However, exercise appears to improve men’s sperm count. Those who took part in the research by the Harvard School of Public Health who did 15 or more hours of moderate to vigorous exercise every week were found to have sperm counts that were 73 percent higher than the least active.
The study is relatively small and a low sperm count does not mean that a man will be unable to father a child, but, the authors say, it could be that semen quality can be improved by a more active lifestyle.
There has been much discussion about whether semen quality has been declining over recent decades, the authors say in their paper, published in the online edition of the British Journal of Sports Medicine.
“Despite the inconsistent findings, the majority of data supports a decline in sperm concentration in most Western countries, and the causes of the observed decline are still debated,” the authors said.
“One possible explanation could be the concurrent decrease in physical activity and increase in sedentary behavior over the same time frame,” they added.
Some studies have suggested that strenuous exercise may damage male fertility, based mainly on studies involving cyclists and long-distance runners.
Although there has been plenty of evidence of the dangers of “couch potato syndrome,” an association between watching TV and lower semen quality has never been investigated, they say.
The 222 participants were among those recruited for the Rochester Young Men’s Study in 2009-2010 in New York. All were healthy and aged between 18 and 22.
Allan Pacey, senior lecturer in andrology at the University of Sheffield, said the authors’ conclusions were plausible. It was possible that testicular heating — through sitting on a sofa for a long time — could decrease sperm counts.
“However, it remains to be seen if coaxing a TV-watching couch potato into doing some regular exercise could actually improve his sperm count, or whether there exists an unknown fundamental difference between men who like exercise and those who do not, which might account for the findings,” Pacey said.