Physical activity levels may affect men’s semen quality

By Sally Robertson, B.Sc.Feb 6 2013

The quality of young men's sperm may be influenced by how active their lifestyle is, report researchers.

Audrey Gaskins (Harvard School of Public Health, Boston, Massachusetts, USA) and colleagues found in their study of 189 young men, that those who performed the highest weekly amount of moderate-to-vigorous physical activity had significantly higher sperm concentrations and counts than those who performed the lowest weekly amount.

In addition, those who watched the least TV each week had substantially higher sperm concentrations and sperm counts than those who watched the most TV each week.

As reported in the British Journal of Sports Medicine, the median weekly amount of moderate-to-vigorous exercise performed by the men was 8.25 hours (interquartile range [IQR]: 5-14 hours/week). And the median amount of time spent watching TV (or videos or DVDs) was 14 hours (IQR: 4-20 hours/week).

Multivariate analysis showed that men in the highest quartile for moderate-to-vigorous physical activity (≥15 hours/week) had a significant 73% higher mean sperm concentration and a 41% higher mean sperm count than men in the lowest quartile for this type of exercise (<5 hours/week).

Similarly, men in the highest quartile for TV watching (over 10 hours/day) had a significant 44% lower mean sperm concentration than men in the lowest quartile (1-3 hours/day), as well as a similarly reduced mean sperm count, reports the team.

"Despite inconsistencies in the literature, an effect of physical activity and inactivity on sperm counts (concentration and total) has biological plausibility," say Gaskins et al.

Exercise that does not lead to exhaustion has previously been shown to increase the expression of antioxidant enzymes throughout the body, notes the team, while physical inactivity on the other hand, has been associated with increased levels of oxidative stress.

"Therefore, regular exercise might work to prevent reactive oxygen species generation and protect male germ cells from oxidative damage," suggest the researchers.

For the study, men were asked about the quantity and intensity of weekly exercise they had engaged in during the preceding 3 months, as well as how much time they spent watching television, DVDs, or videos during that period. Moderate-to-vigorous activity was defined as any exercise that made the men very sweaty or winded and was also determined through calculating the men's metabolic equivalents accrued during the exercises.

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