The cremaster muscle is found only within the male human body and covers the testis. The muscle moves the testis, promoting healthy and motile sperm.
The cremaster muscle lowers and raises the testis in order to control its temperature. When a man enters an environment with a colder temperature, the muscle causes the testis to move against the body. The more the testis presses against the body, the less it is exposed to the cold air. In this position it is also able to warm slowly though body heat.
The cremaster muscle also works during fight or flight scenarios, when the man must either fight or run. The muscle pulls the testis towards the body to protect it.
The cremasteric reflex refers to an action the muscle takes in response to the stroking of the inner thigh. If the hand moves softly along the area from the hip to the knee, the muscle immediately reacts by raising the testis. The reflex may also occur when a man breathes in deeply or contracts his abdomen.