Bones and connective tissues give us structure and support. However, connecting our pieces and parts is of no use if we can’t also move them. This is where the muscular system comes into play.
Muscles turn chemical energy into mechanical energy by contracting across a joint**.** In doing so, they pull the bone they insert upon closer to the bone they originate from. It's important to note that because of this, muscular contraction is always a pull (a contraction). The opposing force to a given movement is generated by an opposing muscle group contracting. For example, forearm lifting is generated by contracting biceps, whereas forearm extension is generated by contracting triceps.
Adapted from: https://commons.wikimedia.org/w/index.php?curid=30015046****
There are three main types of muscle: