Heat-based contraception

An alternative male contraceptive method involves heating the testicles so that they cannot produce sperm. Sperm are best produced at a temperature slightly below body temperature. The muscles around a male's scrotum involuntarily tighten if the man's body temperature drops, and they loosen, allowing the testes to hang, if the body temperature rises. This is the body's way of keeping the sperm at an ideal temperature. This means that sperm production can be disrupted with increased temperature. Some suggest exposure to high temperatures (116 °F equal to 47 °C) can affect fertility for months. Male thermal contraceptive methods (MTC) derive their effectiveness from the alteration of the thermoregulatory function of the scrotum. When this function is altered – by wearing tight underwear, being exposed to a high outside temperature, or by developing a fever, fertility may be impaired. Methods used include hot water applied to the scrotum, heat generated by ultrasound, and artificial cryptorchidism (holding the testicles inside the abdomen) using specialized briefs. One of the initial experiments resulted in partial infertility lasting more than four years. Initial experiments suggest it is effective and safe, though there have not been long-term studies to determine if it has any side effects on the body after reversal.