Question

Levers Lab: What do you notice about the shape of your shoulder muscle? What do you think this indicates?

Answer 1

Let's start from the top- numerous muscles work in synergy for free movement of our shoulder, each in charge of different directions of rotations. The deltoid- This muscle is primarily responsible for giving your shoulder that rounded shape that it has. It stabilizes and moves the shoulder and arm. The deltoid is the main abductor muscle of the shoulder, meaning it moves the arm away from the center of the body. The deltoid has three origin points along the scapula and the clavicle - these bones below: The origin points are stable and do not move, unlike the insertion point of the muscle, below, which moves the humerus bone of the upper arm. The antagonist (or opposing muscle) to the deltoid is the pectoralis major. This muscle is located on the upper chest area and is kind of fan-like in shape. Similar to the deltoid, the pectoralis major has multiple origin points, but just one insertion point. The origin points are below, along the clavicle, sternum, and abdomen, while the insertion point is on the humerus. As the pectoralis major is in the opposite of the deltoid, its function is to adduct the arm, moving it closer to the center of the body.