Scientists at Harvard Medical School have found that men who regularly lift heavy objects at work have higher sperm counts. The research was published in the journal human reproduction.
About 40% of infertility cases are related to sperm quality and quantity. An earlier analysis by the EARTH Research Group found that sperm count and quality dropped by as much as 42% between 2000 and 2017 among men seeking fertility treatment.
The new study included 377 men who came to clinics for infertility treatment. The researchers found that men who frequently lift or move heavy objects at work had a 44% higher total sperm count than those who did less strenuous work.
Men who reported more physical activity at work also had higher levels of the male hormone testosterone and, paradoxically, the female hormone estrogen. Scientists explained that this is due to the conversion of excess testosterone to estrogen – which is necessary to maintain normal levels of both hormones in the body.