The Cremaster Muscle: A Hammock for Your Balls

A marvel of biological design, the cremaster muscle optimizes temperature, comfort and safety for the testes.

ball hammock cartoon

Lighter and more comfortable than tents, hammocks have grown in popularity with back country camping and a buddy of mine is on a quest to construct the ultimate hammock. Following his hammock making adventure and subsequent field tests has given me an appreciation for what it takes to make high quality gear. Engineering is the journey of a 1,000 steps to perfection. With each of a hundred redesigns, my buddy’s hammocks get stronger, lighter and more comfortable.

The cremaster muscle has gone through a similar design process, but one measured in millennia instead of months.

Natural Design: Engineering Perfection

Much like a hammock, the cremaster muscle is an essential component that provides a protected, lightweight, and air-conditioned resting place for the testicles.

Sperm are intricate cells that require a precise environment for proper development. Optimal temperature for sperm production is approximately 93.5 degrees Fahrenheit. Body temperature fluctuates around 98.6 degrees. As medicine has seen in the case of undecended testicles, the testis won’t produce sperm if kept at body temperature. Nature’s response, for warm blooded creatures, place the testicles on the outside. With few exceptions (notably elephants and many marine mammals) all male mammals have testes outside the body.

This solves one problem but creates several others. Outside of the safe muscular-skeletal frame, the sensitive organ is exposed to the elements like a hiker on the Southeastern face of El Capitan. Dangling by a literal cord, the testicle faces potential exposure to cold pools, hot saunas and the ever terrifying shot to the nuts. Nature comes to the rescue by engineering the perfect gear that enables the testicle to complete its sperm making mission while remaining safe and comfortable.

Meet the Cremaster

The cremaster muscle is a muscular sac that envelops the testicle and supports it just like a hammock. The cremaster supports the testicle and does the heavy lifting to keep it safe. Each testicle has its own independently operated cremaster. At the threat of danger or exposure to extreme cold, the cremaster draws the testicle up towards the body. It thickens to provide better insulation and protection. It also contracts during arousal knowing that there might be more jostling than usual. Cremaster has your back.

Diagram of cremaster muscle

When danger has passed, when it is warm or when you are relaxed the cremaster lets go and the testicle hangs loose. Hanging low stretches out the veins and arteries that provide blood to the testicle preventing them from over heating it. It also thins out acting as a natural radiator to diffuse body heat away from testicle and effectively cool it to the perfect temperature.

The Dartos: Cremaster’s Nerdy Little Cousin

To further optimize temperature, the skin of the scrotum is layered onto a muscular layer known as the dartos facia. Ever look at your balls and feel like they are constantly moving? The dartos facia controls how wrinkly the scrotal skin is, fine tuning the structures that radiate heat. Responding the local conditions, the dartos constantly senses temperature and adjusts which is sort of fascinating and strange to watch. It seems as though the testicle has a mind and will of its own.

Good design hides in ordinary places. Thanks to years of evolution, your balls are safe and sound in a hammock that outclasses anything you could find at REI.

Sara SDx

Sara SDx

Editor of Don't Cook your Balls, Co-Founder of, Health Coach and Men's Health Advocate. Passionate about sperm, men's health and helping people build their families.
Sara SDx

Author: Sara SDx

Editor of Don't Cook your Balls, Co-Founder of, Health Coach and Men's Health Advocate. Passionate about sperm, men's health and helping people build their families.

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