Dr. Paul J. Turek from the University of California, San Francisco and his colleagues decided to see if there were any data supporting the lore that hot baths were bad for fertility.

To their surprise, they found scarce data on the subject. This is when they decided to do their own study and see how hot tubs influenced male fertility.

The study included 11 infertile men, around age 36, who regularly used hot tubs or jacuzzi for at least 30 minutes a week. They tested their semen quality before and after they stopped using hot tubs
Three to six months after, five of the men had an average increase in total motile sperm counts of 491%. Those men who didn’t see any improvement in their sperm counts were heavy smokers with a significant smoking history.

The researchers suggest that men trying to conceive should cut down on hot tubs or Jacuzzi’s in order to improve their semen quality and regain their fertility. They also say that an overall health is important in semen production as a normal healthy man makes 1,200 sperm per heartbeat. That kind of activity requires a fast running engine and a healthy body.