Anatomy and Physiology: The Dancer's Alphabet

The Dancer's Alphabet

This title is an interesting analogy. No matter how glorious a dance is, it can be broken down into simpler parts. Many of a dancer's movements are combinations of many of the simple movements to follow. Given that all of the glory of literature in English, from Shakespeare, to Poe, to Swift, to Austen, to Dickens, to Dickinson, to Hiaasen, to, well, you name it, is all based on a brilliant juggling of the same 26 letters, I think it is safe to say that the analogy holds.

As you learn these movements, keep thinking in terms of opposites. The muscles that control these movements are found in what are called antagonistic pairs, and so it is only natural that the movements fall into pairs as well. Given all of the directional terms you learned, this should be second nature to you. Don't plan on memorizing and forgetting these movements, by the way, because you will be using them, along with the directional terms and the names of the bones, whenever you learn muscle names. So? Let's get movin'! The following table provides an overview of the movements at synovial joints.

A New Angle

One of the things I have to unteach every year is the idea that flexing and contracting is the same thing! Flexing is only one in a number of movements described as angular. Angular motion is, quite simply, motion in which one end of the bone is stationary, but the diaphysis, or shaft, of the bone changes its angle. First of all, we need to refer to the body in anatomical position, with the palms facing forward, and the arms, legs, back, and neck straight. Why? Because angular motion, including flexion, is motion relative to anatomical position.

When you stand in anatomical position, the bending of any joint that decreases the angle of that joint is known as flexion (see Figure 7.2). For example, in anatomical position, your arm, as a straight line, is a 180-degree angle; if you bend your elbow, to make your forearm parallel to the ground, you have a 90-degree angle. That is an example of flexion, as is the bending of the knee in the Hollywood foot-poppin' kiss. Don't forget fingers and toes!

Figure 7.2Flexion, extension, and hyperextension. (LifeART©1989-2001, Lippincott Williams & Wilkins)

Extension, on the other hand, is simply the return of the joint to anatomical position. An extreme version of this is called hyperextension, when movement in the direction of the extension is continued, but beyond anatomical position. In some joints, such as the elbow and knee, such movement involves injury; just thinking about landing badly on the knee and having it bend forward instead of back is a creepy thought! Other joints, however, do this freely, as you do with your head when you look up at the sky. You hyperextend your leg at the hip every time you walk; you do the same thing with your arm if you swing your arms while you walk!

Abduction and adduction are similar, except the movement is along an entirely different plane of the entire arm or leg (in which (see Figure 7.3). Flexion and extension act on a the elbow or knee may remain sagittal plane, with the movement always in the straight)! Flexion and extension anterior/posterior direction. Abduction and adduction, on the other hand, act along a frontal plane, with the movement in a lateral/medial direction. Abduction and adduction are the domains of ball-and-socket joints at the pelvis and shoulder, and the saddle joints at the base of each finger.

Figure 7.3Abduction, adduction, and circumduction. (LifeART©1989-2001, Lippincott Williams & Wilkins)

It is easy to remember the difference if you look at the root of the words. Abduction comes from the root abduct, which means to “take away.” The movement of your arms up and your legs wide at the start of a jumping jack is a classic example of abduction. Adduction, on the other hand is the opposite motion, to add the arms and legs to the body, as when a, soldier comes to attention. Circumduction, as its name implies, involves a circular motion, as you would when you swing your arms, such as in the windup to throw a ball (see Figure 7.3). This movement, in a limited fashion, happens at ellipsoidal and saddle joints, but it is best done at ball-and-socket joints.

Excerpted from The Complete Idiot's Guide to Anatomy and Physiology © 2004 by Michael J. Vieira Lazaroff. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

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