Watching more than 20 hours of television a week almost halves the fertility of healthy young men, according to a new study out last night.
And doing 15 or more hours a week of moderate to vigorous exercise results may make men much more fertile than those who do just a little exercise, the research published in the latest edition of the British Journal of Sports Medicine claims.
The Harvard School of Public Health, Boston, Mass, USA, analysed the sperm quality of 189 men between the ages of 18 to 22 in 2009-10, all of whom were from Rochester in New York State, USA.
More than half the men were within the normal weight range for their height, and three quarters were non-smokers.
They were each asked about the exercise they had done in the preceding three months, and how much time they had spent watching television, DVDs, or videos over the same period.
Factors that might affect sperm quality, such as medical or reproductive health problems, diet, stress levels, and smoking, were taken into consideration. The prevalence of reproductive health problems was low.
Those who were the most physically active – undertaking 15 hours or more exercise a week – had a 73% higher sperm count than the least physically active, but exercise did not affect sperm motility, shape, or sample volume.
Light physical exercise, regardless of how frequently it was undertaken, made no difference to the sperm count.
However, television viewing had the opposite effect. Those who watched 20 or more hours had a sperm count that was 44% lower than those who watched the least. Again, there was no impact on sperm motility, shape, or sample volume.
The authors point out that a reduced sperm count does not necessarily curb a man’s fertility or his chances of being able to father a child. However, a more physically active lifestyle may improve semen quality.
The type of exercise might also be important, say the authors.
“Future studies should also evaluate the extent to which different exercise types affect semen quality as previous studies suggest that there might be opposing effects of different types of activity on semen characteristics,” they add.
Gaskins A, Mendiola J et al. Physical activity and television watching in relation to semen quality in young men. Br J Sports Med. 4 February 2013.doi:10.1136/bjsports-2012-091644 [abstract]
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