I also read that if you wanted your testicles to work properly you should keep them cool at all times. One suggestion involved wearing loose clothes – preferably boxer shorts, and for nighttime, pajamas or nothing at all below the waist. I also heard that holding the testicles in cold water for a minute or two every day (e.g., after a shower) will noticeably increase your sperm production (after a two- or three-week delay). Is there any truth to this?
It's true that sperm production requires a slightly lower body temperature, and there may be some truth to the theories about boosting sperm production – but you have to distinguish between sperm production and semen production. Sperm cells, which are all produced in the testes, account for only a portion of a given volume of semen – and much of the rest of semen is produced not in the testes but elsewhere. (For more information, see SEMEN PRODUCTION & EJACULATION in Science Corner.) So even if you were able to increase the number of sperm cells in your semen, the total volume of an ejaculation might not noticeably increase.