In the next few articles, I am going to focus on shoulder, neck, upper back and chest muscles and their motions. The purpose is to give the reader a common "user friendly" overview for troubleshooting issues with upper body. I would advise to think about the motion that causes the problem and then look a little deeper into the muscles involved in the motion. Usually, it is not just ONE muscle that is causing problems, but a few muscles or groups of muscles involved. As you read you will notice some muscles have the same actions. Also, I find it very hard to breakdown scientific jargon of other components, in the human body, without overloading this article with colorful metaphors and abstract examples. SO, I am not going in to bone, cartilage or tendons, which can easily be part of the problem.
I will start with the well known bigger muscles involved. These muscles are the main action makers. The next article, I will go a bit deeper and explain the assisting muscles. Assisting muscles are usually strained, misused and overused for different reasons. However I will give you the big guys first then we'll go into the little ones:
The shoulder head itself.....Deltoid (Anterior/Lateral/Posterior)
Wraps around a third of the collar bone to the top bony ledge of the shoulder blades. Extends almost halfway down the upper arm bone.
Common Actions
Anterior Deltoid - rotates the arms inward through the "ball and socket" shoulder joint. Also swings arms overhead and in front of your body. It pulls the shoulders forward while spreading the shoulder blades for that "I'm tougher then I really am" look.
Posterior Deltoid - rotates the arm outward (towards your back). If the arm is over head it swings the arm back down and behind the body. Pulls the shoulders back and squeezes shoulder blades together (so the chest appears to be pushed out).
Lateral Deltoid - swings the arm out to the side, up and overhead as if you had wings.
Pectoralis Major (Chest)
Goes from the lower side of your collar bone and most of the breast bone (which is right in the middle of your rib cage) and attaches to the upper arm bone. It also lays across and attaches to the first seven ribs.
Common Actions
Squeezes itself together towards your breast bone. If you swing your arms in front of your body like your going to bear hug a bear, you are using this muscle primarily.
It also rotates your shoulders forward as if you are doing bodybuilders flexing chest pose.
Trapezius Upper/Middle/Lower (Traps)
Goes from the skull, along the spine, and down to your middle back. It stretches across the back of your collar bone to the bony point at the end of your collar bone. It squeezes between the shoulder blades all the way done to the bend in your back where middle back meets lower back.
Common Actions
Upper and middle - Squeezes the shoulder blades together pushing out the chest.
Upper - It also "shrugs" your shoulders up towards your ears. Assist in heavy breathing and very hard laughing.
Upper - Also it pull your head back with chin facing up and can twist your head to either side.
Lower - It can also do the exact opposite motion of pulling your shoulders down towards your waist.
Lots of actions!
Latissimus Dorsi "Lats"
Sweeps up from the mid to low back, lays across the backside of most of your ribs (in mid to low back), and attaches to the upper arm and shoulder blades.
Common Actions
This very large muscle swings the arms downward and back behind you. It also can make a big squeeze like action in your back forcing your chest out and upwards. Once again helps you out with breathing if needed.
Biceps Brachii (Biceps) Short/Long head
Short head starts from the inside of the tip of the shoulder blade (closest to your upper arm bone), while the long head starts at a lower point on the shoulder blade close to your armpit and in an area between your shoulder blade and upper arm bone. Both will end around the junction between your upper and lower arm bone and on one of your forearm bones called "radius".
Common actions
I think you already know one action. It curls, dude! Known to trainers as elbow flexion. It also assist with swinging your arms upward (especially if you are holding something with weight, like your baby). It likes working with the your palms of your hands facing forward the most.
Triceps Brachii (triceps) Long/Lateral/Medial Heads
Long head starts at the lower inside portion of your shoulder blade closest to upper arm bone and the other two heads are starting from your upper arm. All heads will end on one of your forearm bones called the "ulna".
Common Action
Mainly taking your arm from a bent position (from the elbow) to a straight position. Also helps out to swing your arms backwards and stabilize or hold arms straight.
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