you can feel it

Hi Bryan Wong,
Skeletal muscles when contracting, usually "bunch up" get shorter and harder. Interestingly when one skeletal muscle relaxes, another opposing muscle is usually contracting.
When walking, or running, groups of muscles work in tandem, balancing, striding, pulling the leg back, putting the leg forward, putting the foot, the lower leg the toes, the hips, the ankles, all in the best position for each part of the act of movement that the brain has requested. We learn these movements as children, and unless we have a brain injury requiring relearning, we will remember without having to think consciously how to do it for our whole lives.
When we are unconscious, most skeletal muscles relax. Thus a person who is knocked out, or faints, falls limply to the floor, since none of the muscle pairs or groups are working together to keep the person upright and balanced in a standing or even sitting position.
Even sitting still at your computer, your muscles are working to support you, your eye muscles are working to focus and moving across your screen and your finger muscles are operating to strike the keyboard. All thes little actions require contractions and relaxations of opposing pairs or groups of muscles working smoothly and in tandem action without direct conscious thought. Some people shake their foot while sitting still, too, so some of their foot muscles are contracting and relaxing even without the person realizing they are doing that.