Researchers found men who worked out more had faster swimming sperm that was better formed, compared to their sedentary peers.
They suggest that exercise promotes healthy hormone levels that create a better environment in the testes for sperm production.
The findings, from the University of Cordoba in Spain, are important because semen quality has dropped overall in the last 50 years. Many factors have been blamed including drinking, smoking, and the rising levels of obesity.
The team assessed whether there was any difference in the hormonal levels and semen quality of men who were physically active compared to those who weren't.
They looked at factors including sperm count and mobility and analysed hormones including testosterone, cortisol and the follicle-stimulating hormone.
The results concluded physically active subjects display better semen values.
Research leader Diana Vaamonde, said: 'Despite the fact that the sample population is not very big (31 men), given the complexity of the analysis, this is the first study that assessed the differences between these parameters in both populations.
'Despite that fact that more studies are needed to confirm these findings, we can suggest exercise to improve the hormonal environment and stimulate the sperm process.'
However, it may be true that doing too much exercise could have a counter-productive effect.
In 2010 Vaamonde published a study showing that the sperm parameters of elite sportsmen are worse than men who are just physically active. It is possible that the increased strain of training causes a decline in sperm quality.
The latest study was published in the 'European Journal of Applied Physiology.'
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