Skeletal muscles are mainly used to protect bones, maintain normal posture, and enable the body to produce movement effects. 1. Protecting bones: Skeletal muscles are located in the outer layer of bones, and can buffer the force when the body parts are subjected to violence and other stimuli to protect the bones from injuries caused by external blows. 2. Maintaining normal posture: Skeletal muscles can be categorized into prime mover, antagonist, synergist, and fixer muscles, and when these muscles play their roles against each other, they can enable the body to maintain normal posture. 3. Make the body produce movement effect: the thicker part of skeletal muscle is called muscle belly, the thinner part is called tendon, skeletal muscle under the action of the nervous system to make the muscle belly, tendon and bone in the skeletal muscle contraction to produce movement effect.