Men who watch a lot of television have lower sperm counts than those who don’t watch any, researchers report February 4 in the British Journal of Sports Medicine . Sperm count is an informal term that refers to the concentration of sperm in a given volume of semen.
Researchers gave questionnaires to 189 healthy young men and analyzed their semen.
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Respondents who watched more than 20 hours of TV per week had 44 percent lower sperm counts than those who didn’t watch any. The team, led by Audrey Gaskins and Jorge Chavarro of the Harvard School of Public Health, also found that men who spent the most time doing moderate to vigorous physical exercise had 73 percent higher sperm counts than did the men who were least active.
While the findings don’t spell out an explanation for these differences, the authors cite the broad physiological benefits of exercise. Cooler scrotal temperatures have been linked to a higher sperm count, and that sedentary positions and certain exercises such as bicycling have been linked to higher scrotal temperatures.

*source:- http://www.sciencenews.org/view/generic/id/348066/description/News_in_Brief_TV_watching_linked_to_low_sperm_counts