most helpful answer testicles inside the scrotum are biologically designed to remain cooler. since this lower temperature is more optimum for the preservation of sperm. any underwear that compresses the scrotum closer to the body tends to increase heat and may reduce sperm count. so the answer would be loose boxer's or if the man dares go "commando" and wear none at all.
which men's underwear is biologically healthier the boxer or the boxer brief (the tight one) with regard to fertility? . which men's underwear is biologically healthier the boxer or the boxer brief (the tight one) specifically with regard to fertility? .