There are three types of muscles in use in the human body. Cardiac Muscle is the muscle that makes heart. Myocardium (cardiac muscle) is designed by the body to be able to constantly contract and expand in rapid succession, without stopping (trust me you wouldn't want it to stop). In order to maintain homeostasis the muscles of the heart require a lot of oxygen and glucose to keep up with the usage, to which the heart connects directly to Aorta and siphons off oxygen rich blood. The cardium also provides a major example of homeostasis because the blood that it pumps keeps us alive.
The two other muscles are the Smooth and Skeletal Muscle. If you want an example of why smooth muscle is important, than all you have to do is think about eating. The GI tract is composed of a lot of smooth muscle, and without it you wouldn't be able to gain any nutrition.
Skeletal muscle is the muscle that you can control, and is the muscle that you can show off when you flex. Skeletal muscle is crucial toward movement and support. Without it you'd be a skeletonized human worm.
