The sarcomere is the basic unit of a striated muscle and the force of a muscle is directly related to the extension that the sarcomere is under. When a sarcomere is extended from 1.5 micrometres to about 3 micrometres, the muscles' force is great and max at about 2/2.5 micrometres. When the muscle is fully extended and, therefore, the sarcomere is extended over than 3 micrometres, the muscle force decreases exponentially.