As a fitness professional and an exam candidate, there is no way of getting around the fact that you need to know your anatomy! Understanding how the body moves and creates movement with the muscles is a huge part of the job. In an earlier blog, we looked at how to study anatomy. We then started breaking down each body part, with the last blog looking at the muscles that move the scapulae. Here, we will look at the muscles that move the arm at the shoulder, elbow and wrist joints. Shoulder Joint The glenohumeral joint (commonly referred to as the shoulder joint) consists of the humerus bone attaching into the scapula. Many actions occur at this ball-and-socket joint. Action of the Shoulder What the Action Looks Like (Move Your Body!) Primary Muscles Shoulder abduction Lift your arms out to the side Deltoid – all fibers Shoulder adduction Lower your arms to your side Pectoralis major and latissimus dorsi Shoulder flexion Lift your arms in front of you Pectoralis major, and anterior fibers of the deltoid Shoulder extension Lower your arms from lifted or lift your arms behind you Latissimus dorsi, teres major (“little lat”) Internal shoulder rotation From the anatomical position, twist your arms so that the knuckles of your hand face forward. This action at the shoulder can occur when your arm is in different positions (flexion, abduction, etc.) Subscapularis Latissimus dorsi and pectoralis major also play a role in internal rotation External shoulder rotation From the anatomical position, twist your arms so that the knuckles of your hand face backward. This action at the shoulder can occur when your arm is in different positions (flexion, abduction, etc.) Infraspinatus and teres minor Horizontal abduction For the start postion, lift your arms in front of you. The action occurs as you then move your arms out to the side Latissimus dorsi and posterior fibers of deltoid Horizontal adduction For the start position, lift your arms out to the side. The actions occurs as you then move your arms in front of you Pectoralis major and anterior fibers of deltoid Elbow and Wrist Joints The elbow joint consists of the humerus bone and the radius and ulna bones. The two main actions at the elbow are flexion and extension. The wrist joint consists of the distal ends of the radius and ulna and the carpal bones of the hand. The two main actions of the wrist are flexion and extension. Action of the Elbow and Wrist What the Action Looks Like (Move Your Body!) Primary Muscles Elbow flexion Bend your elbow Biceps brachii Elbow extension Straighten your elbow Triceps brachii Wrist flexion Bend your hand towards your forearm Wrist flexors Wrist extension Bend your hands backwards Wrist extensors A helpful way to learn the muscles is to get up out of your chair and move and mimic the actions for the muscles you are learning that week. Look at the picture of the muscle, find it on your body, and picture how the muscle is contracting and what muscles are involved in the movement. Make the muscle contract and complete the different actions that muscle is involved in. Stay tuned for our next blog in this series, which will discuss the muscles of the core. If you have any additional questions that were not answered in this blog, please don't hesitate to contact our Resource Center at 1-888-825-3636 ext. 796 or firstname.lastname@example.org.