Human sperm race to fertilize an egg. David M. Phillips/Science Source Guys, it may be time to get off the couch and hit the treadmill — especially if you want to have kids. Okay, we all know that exercise is good for us. It can reduce the risk of obesity, diabetes and heart disease, to name a few benefits. Now researchers say physical activity may also help keep sperm healthy and happy. A study published Monday in the British Journal of Sports Medicine suggests that how physically active a guy is can affect his total sperm count and sperm concentration. Researchers surveyed 189 young men (ages 18 to 22) on their exercise and TV-watching habits over a three-month period. They also collected and analyzed the participants' semen. Men who watched 20 or more hours of TV per week had a sperm concentration 44 percent lower than those who watched almost no TV. On the other hand, men who exercised more than 14 hours per week had a sperm concentration 73 percent higher than men who exercise