The Shoulder, Part IV

FINE
BY SUSAN L. HITZMANN, MS

ANATOMY

The Shoulder, Part IV
Dynamic shoulder movements in the horizontal plane.
The past three Fine Anatomy articles have examined movements of the shoulder and the shoulder girdle. Because the shoulder is an immensely complex structure, personal trainers must invest a significant amount of time and effort learning its “functional pathologies” and understanding basic anatomy in order to create sound exercise program design. Over this series, primary movements such as flexion, extension, abduction, adduction and rotation have been discussed. Although there are many other movement factors to consider in assessing the overall function of the shoulder, each of the past three articles provides insight into the movement “potential” the shoulder joint can obtain without obstruction. This article wraps up the series by taking a look at dynamic shoulder movements in the horizontal plane (arm at 90 degrees from neutral, or 0 degrees from anatomical position). Each of the muscles discussed has already been cited over the course of the series, which has included detailed anatomical illustrations and charts that define muscle origin, action and insertion (see”Resources”on the next page). This article will sum up the dynamic range and “put the pieces together” to explain circumduction of the shoulder, which combines movements in all planes.
IDEAL MOVEMENT

scapular positioning. If pectoralis major, pectoralis minor or serratus anterior becomes adaptively shortened, the shoulder girdle (unilaterally or bilaterally) will be set slightly anterior, or forward. This will cause a change in range of motion (ROM) of both the shoulder girdle and the humerus. Assuming this postural stance will limit shoulder ROM; movements will not look ideal, nor will they necessarily be executed properly. Many clients will need exercises broken into smaller motions before they can integrate the movements properly.
HORIZONTAL ABDUCTION AND ADDUCTION

can be achieved. Anterior deltoid and pectoralis major are the primary movers of the arm in this motion.
ROM IN TRANSVERSE PLANE

Movements of the shoulder girdle in the transverse (horizontal) plane involve movements of the scapula on the thorax. Ideally, the shoulder girdle should move easily backward or forward from neutral. If the shoulder girdle is set slightly posterior to neutral or slightly anterior, the movements of the humerus–such as rotation–will be altered owing to both glenohumeral and

Horizontal abduction and adduction are movements in the transverse plane about a longitudinal axis. Horizontal abduction, also known as horizontal extension, is movement in a lateral and posterior direction 30