There's another reason for men to hit the gym, with new research saying that men who are more active have faster swimming sperm.
The Spanish study shows that exercise promotes healthy hormone levels and creates a better environment in the testes for sperm production.
Professor Diana Vaamonde, from the University of the Cordoba Medical School, looked at sperm count and mobility and analysed hormones including testosterone, cortisol and the follicle-stimulating hormone in her subjects.
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She compared 15 inactive men with 16 physically active subjects.
The active men were shown to have faster swimming semen, with a higher sperm concentration as well as larger semen volume.
As part of the study, the participants were asked to abstain from sexual intercourse and to exercise a few days prior to testing.
"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," said Dr Vaamonde.
"We have analysed qualitative semen parameters like the ejaculated volume, sperm count, mobility and sperm morphology. But despite the fact that more studies are needed to confirm these findings, we can suggest exercise to improve the hormonal environment and stimulate the sperm process."
Dr Vaamonde's study also suggests that semen quality has dropped over the last 50 years, with drugs, alcohol and obesity being the main culprits.
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However, there are warnings not to go too far, as excessive exercise may have the opposite effect.
In 2010, Dr Vaamonde found high levels of exercise affected the fertility in both men and women, especially elite cyclists.
She said heat, wearing tight clothing, friction of the testes against the saddle and stress on the body from rigorous exercise could contribute to poor sperm quality.
This study was published in the European Journal of Applied Physiology.
Author: Bernadette Chua
Approving editor: Philippa Lees.