Sperm are finely crafted little baby making machine, and they require a precise environment. Human testes cannot function properly unless they are able to stay cooler than the rest of the body. Thankfully, the male anatomy is designed to create distance between the testes and the core body temperature. Testicles were fitted with a muscle called the cremaster muscle, which contracts to pull the testicles close to the body when they get too cold and relaxes to let them hang lower when it gets warm.

If the temperature of the testicles is raised to 98˚, sperm production ceases. When production is interrupted, sperm can be negatively impacted for months. Any time sperm production is interrupted, it can take months for sperm to rebound. This will show up on a semen analysis as reduced motility. If the exposure to heat is prolonged, it can affect sperm production processes, causing the body to produce fewer sperm, many of which may be abnormally shaped. On a semen analysis, this will show up as reduced sperm count and abnormal morphology (often accompanied by reduced motility).

Those at risk includes, but not limited to; bakers, long distant drivers, motorcycle riders etc.