Scientists at Harvard Medical School have found that men who regularly lift heavy objects at work have higher sperm counts. The study is published in the journal Human Reproduction .
About 40% of infertility cases are related to the quality and quantity of sperm. A previous analysis by the EARTH Research Group found that among men seeking fertility treatment, sperm count and quality decreased by as much as 42% between 2000 and 2017.
The new study involved 377 men who applied to clinics for the treatment of infertility. The researchers found that men who frequently lifted or moved heavy objects at work had a 44% higher total sperm count compared to those who did less strenuous work.
Men who reported more physical activity at work also had higher levels of the male sex hormone testosterone and, paradoxically, the female hormone estrogen. Scientists explained that this is due to the fact that excess testosterone is converted into estrogen – this is necessary to maintain normal levels of both hormones in the body.