Men with ambitions of fatherhood, meanwhile, should chuck out their Y-fronts, skin-tight jeans and cycling shorts and replace them with loose-fitting boxer shorts - or, better stukkm "go commando".
That's because wearing tight pants can cause infertility and damage to the testicles. In the 16th century, Russian peasants actually used bearskin pants as a method of birth control.
"Testicles hang in the scrotum to keep cool - they need to be 22°C cooler than the core body temperature," explaints Dr Richard Petty, men's health expert at the Weymouth Street Wellman Clinic in London. "If men wear tight underwear or trousers, the testicles become too hot and both testosterone and sperm production decrease - a common reason for male infertility.
"Wearing tight pants also puts pressure on the testicles, pushing them up against the body or into pouches within the body. This can cause sore, painful testicles. There is also evidence to suggest that there could be an increased risk of testicular cancer."
Men's pants are modern invention. In the past, men tucked their shirt tails between their legs and fastened them with buttons. Y-fronts were invented for baseball players in 1932 and boxer shorts as a healthy uniform pant for soldier in World War II. Petty says his father - also a doctor - never wore underpants because of the known health risks
