If you enjoyed the usual American male weekend of constant television viewing while sunk deep in the pizza-crush folds of your sofa, evolution has already decided it doesn't want your kind in the generations to come. That's why low-activity men who watch lots of television have dramatically lower sperm counts than those who get some exercise.
The subjects of the study were college-aged men in New York state, aged 18-22. The first group did 15 hours of "moderate to vigorous physical activity per week," about 2 hours daily. The second group just slobbed out in front of the flat screen for 20 or more hours weekly. Besides being incredibly dull people, the latter group also had remarkably lower sperm counts than those who exercised. The active men had 73% more sperm than the couch sloths.
Clocking up 20 hours a week of TV time appears to be detrimental, the US authors from Harvard say in the British Journal of Sports Medicine. Yet 15 hours or more of exercise a week boosts semen quality, according to the results in nearly 200 college students.
Sperm counts have been declining in developed nations for years now, although not enough to affect the ability of these lethargic males from reproducing. Eventually, however, when climate change has made the Earth a water-covered globe with a few heavily populated islands, those men with the higher sperm counts will have an advantage in the annual "try to have a baby" lottery.