For those men who are looking to boost their sperm count, researchers at the Harvard School of Public Health have some simple advice: drop the TV remote control and get to the gym.
A study published Monday in the British Journal of Sports Medicine found that men who watched more than 20 hours of television a week had 44% lower sperm count than men who watched almost no television.
Researchers found too that men who engaged in moderate to vigorous exercise for 15 or more hours a week had 73% higher sperm count than men who exercised less than five hours per week.
The findings come amid claims from some scientists that sperm quality has declined among Western men in the last decades. Some say it may be due in part to a rise in sedentary lifestyles.
"We know very little about how lifestyle may impact semen quality and male fertility in general, so identifying two potentially modifiable factors that appear to have such a big impact on sperm counts is truly exciting," said lead author Audrey Gaskins, a doctoral student at HSPH.
The study was based on 189 men in Rochester, NY. Study subjects, who had an average age of 19, were surveyed on their television viewing habits, exercise regimen, tobacco use and diet. Samples of their semen were then analyzed for sperm concentration; sperm motility; sperm morphology, or shape; and total sperm count.
While more exercise and less TV were closely associated with higher total sperm count and concentration, they appeared unrelated to sperm motility or morphology, according to the report.
Reduced sperm count has been linked to lower fertility. However, it does not absolutely prevent men from fathering a child, authors said.
"The majority of the previous studies on physical activity and semen quality had focused on professional marathon runners and cyclists, who reach physical activity levels that most people in the world cannot match," said senior author Jorge Chavarro, an assistant professor of nutrition and epidemiology at HSPH.
"We were able to examine a range of physical activity that is more relevant to men in the general population," he said.