And this involves two very important types of muscles, the biceps muscle and the triceps muscle as well as all these bones as shown in the diagram. So basically this is our bicep muscle, this bone is the humerus bone and the muscle behind the humerus bone is our tricep muscle. Now when we actually create this motion, what happens is the humorous muscle does not actually move or the humorous bone does not actually move. And this bone is known as our immovable bone. While the bone inside this portion of the arm do actually move with respect to our body. So the bones inside this are the radius bone and our ulna.