The researchers studied how cadmium affects rat sperm movement using a computer analysis system. They gave rats different amounts of cadmium and checked their sperm. High doses of cadmium made sperm production decrease a lot. Medium doses made sperm movement decrease. The highest dose made sperm stop moving completely. This shows that cadmium can harm the cells that make sperm, affecting sperm movement even before sperm production is affected. Sperm movement is a good way to see how cadmium can harm male reproduction.