Why Are Muscles Always Moving

Your muscles are always moving. It is impossible to sit still. Your heart is always pumping, and your muscles make you breath and hold you upright. If your muscles all relaxed at the same time, you would collapse. You would not be able to survive without your muscular system.
There are three types of muscle in your body: smooth muscle, cardiac muscle, and skeletal muscle. Smooth muscle is located in the digestive tract and in the walls of blood vessels. It moves food through the digestive system. Cardiac muscle is found only in the heart. This muscle pumps blood throughout your body. Skeletal muscle is attached to your bones to help you move.
Muscle action can be voluntary or involuntary. The muscles that you control are voluntary and the muscles that you do not control are involuntary. Smooth muscle and cardiac muscle are both involuntary muscles. Skeletal muscles can be voluntary or involuntary. An example of this is blinking, or swinging your arms when you walk.
You can see many of these movements in everyday life by watching someone raise their hand or even someone smiling or frowning. Signals travel from your brain to your skeletal cells when you wish to move. Then, the cells get shorter, or contract.
Tendons attach your skeletal muscles to your bones. Tendons are tough strands of connective tissue. When a muscle that is connected to two bones contracts, it pulls on the tendon which pulls on the bone. An example of this is the bicep. Tendons attach the bicep to a bone in your forearm and to a bone in your shoulder. Your forearm bends toward your shoulder when your contract your