![]() ![]() This movement shows the joint action(s) of that muscle.įiguring out a joint action with these two steps is simple with a uniarticular (one joint) muscle crossing the center of a hinge joint. This is its line of pull-the direction a muscular force exerts on a joint.Ģ.Bend and/or rotate the joint under the muscle you just traced in the direction of its line of pull. If you know the origin and insertion of a muscle, you can assess its joint action(s):ġ.Draw a line between the origin and insertion of a muscle on the joint it crosses. This knowledge is also essential for isolating the contraction of a specific muscle during palpation, when we direct our clients on how to contract that muscle. These techniques include passive stretching and resisted movement assessments, as well as muscle energy techniques such as post-isometric stretching. Your back muscles, for example, are stabilizers when they are keeping your posture sturdy.Massage and Bodywork Magazine for the Visually Impaired - Assessing Joint Actions Back to Massage and Bodywork Issue List November/December 2013 Issue Back to November/December 2013 Article ListĪssessing Joint Actions By Mary Ann Foster Ī number of massage techniques require an understanding of what actions a muscle produces at a given joint. ![]() Stabilizers act to keep bones immobile when needed. Synergists are muscles that assist the prime mover in its role. One or more synergists are often involved in an action. Prime movers and antagonists are often paired up on opposite sides of a joint, with their prime mover/antagonist roles reversing as the movement changes direction. An antagonist muscle is in opposition to a prime mover in that it provides some resistance and/or reverses a given movement. The prime mover, sometimes called the agonist, is the muscle that provides the primary force driving the action. While many muscles may be involved in any given action, muscle function terminology allows you to quickly understand the various roles different muscles play in each movement. Muscle Actions Have Prime Movers, Synergists, Stabilizers, and Antagonists The biceps brachii, brachialis, and brachioradialis flex the elbow.ĭorsiflexion and plantar flexion You dorsiflex your feet to walk on your heels, and plantar flex them to tiptoe.ĭorsiflexion: bringing your foot upward toward your shin. The triceps brachii and anconeus are muscles that extend the elbow. Below the common terms are listed and defined, with animations to help you picture the muscles and joints in motion.įlexion and extension are usually movements forward and backward from the body, such as nodding the head.įlexion: decreasing the angle between two bones (bending).Įxtension: increasing the angle between two bones (straightening a bend). These muscle actions are often paired, like flexion and extension or abduction and adduction. ![]() The muscles surrounding synovial joints are responsible for moving the body in space. Muscles Act on Synovial Joints to Move the Body The triceps brachii happens to have four points of attachment: one insertion on the ulna and three origins (two on the humerus and one on the scapula). If the place is on the bone that moves during the action, the attachment is called an insertion. If the place is a bone that remains immobile for an action, the attachment is called an origin. Muscles Attach to Bones At Locations Called Origins and InsertionsĪ skeletal muscle attaches to bone (or sometimes other muscles or tissues) at two or more places. Keep reading to learn what all the other muscle jargon means! 1. This muscle plays a big role (that’s what prime mover means) in extending the elbow joint from a bent to a straight position. What does all that textbook jargon mean? The triceps brachii has four places where it attaches to the scapula, humerus, and ulna. The anconeus acts as a synergist in elbow extension. Here is an example: The triceps brachii has three bellies with varying origins (scapula and humerus) and one insertion (ulna ). In textbooks and lectures these details about muscles are described using specialized vocabulary that is hard to understand. Learning the muscular system often involves memorizing details about each muscle, like where a muscle attaches to bones and how a muscle helps move a joint. There are over 600 muscles in the human body. ![]()
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