Propelling and mixing food in the digestive tract is an example of a function of the muscles. Propelling blood is an example of a function of the muscles of the heart. muscle is responsible for for locomotion, facial expressions, posture, respiratory movements, other types of body movement. The capacity of the muscle to be stretched beyond its normal resting length is called extensibility, while the ability of muscle to recoil to its original resting length is called . The capacity of muscle to respond to a stimulus is excitability, and the ability of muscle to shorten forcefully is .