Thus, the tissue becomes stiffer as it is lengthened. Ultimately, enough stretching causes the tissue to break. Since humans have so many different movement needs, the body also has many different types of muscle, which are specialized to perform various tasks efficiently, such as moving food through the digestive tract, pumping blood, running, and so on. Some muscles are called upon to execute rapid movements, such as the eye muscles and the laryngeal muscles. In addition to allowing us to speak and sing, the larynx also performs the vital function of protecting the airway, and must therefore be extremely quick to react.
Different muscles get their unique properties from the composition of muscle fiber type.
Check out the external link to the Washington University School of Medicine website. It presents a nice animation of muscle fiber contraction. In order for muscles to contract, motor units of muscle fibers are recruited. Each motor unit comprised of a number of muscle fibers, and is activated as a whole by a nerve cell. In order to generate stronger and stronger muscle contractions, the number of nerve impulses sent to the motor units, their firing rate , is increased.