Tight fitting underwear like boxers or briefs are obviously very popular choices for guys. However, if you are thinking of starting a family, or fathering another child, then tight underwear is not for you. Studies have suggested that tight underwear may have a negative impact on sperm count as well as sperm quality.
Sperm is manufactured in the testicles which are situated outside the body. This applies to all male mammals – humans and animals alike.