Columns: Do It Right
TYPE OF EXERCISE
The prone shoulder I exercise, also known as shoulder extension in external rotation, is one of four very basic activities known as the T-Y-I-W series of upper body exercises typically performed in a prone position, which activate and strengthen posterior shoulder girdle muscles.
The humerus (upper arm) is actively extended at the shoulder joint while the scapula concurrently is rotated downward, anteriorly tilted and retracted by the infraspinatus, teres minor, deltoid (primarily the posterior fibers), trapezius (middle and lower fibers), rhomboids, levator scapula, and pectoralis minor muscles, respectively, during the prone I exercise. The shoulder girdle muscles activated during the prone shoulder I exercise appear in Figure 1.
BENEFITS OF THE EXERCISE
The prone I exercises activate muscles that provide dynamic stability, optimal muscle length and tension, and proper positioning of the scapula and shoulder girdle on the thorax during upper extremity activities (1–3). Because the arms remain at the sides and below shoulder height, high levels of lower trapezius and minimal amounts of upper trapezius muscle activation occur during the prone shoulder I exercise. Functional imbalances between the upper trapezius and the lower trapezius, middle trapezius, and the serratus anterior muscles have been associated with conditions like shoulder instability and subacromial impingement syndrome, which can cause shoulder pain and dysfunction (1–8). The prone I exercise requires no elevation of the shoulder and can be modified and performed in a standing or supine, hook lying (on the back with 90 degrees of hip and knee flexion) position by pulling either resistance bands/tubing or cables attached to a selectorized weight stack downward from approximately eyebrow level. It is an appropriate exercise for both novice and highly trained individuals. The standing position is appropriate for clients not able to either exercise comfortably or safely in a prone position or on the floor. The prone I exercise will be described in a subsequent section.
Exercises to promote shoulder girdle stability are integral components of strength and conditioning, rehabilitation, and postrehabilitation exercise programs for people who perform repetitive overhead motions during sports or occupational activities (1–3,7,8). This article is not meant to help readers diagnose or treat shoulder pain or injuries. Clients should be free of shoulder or upper extremity injuries and related pain before performing these exercises. The onset of injury-related pain warrants termination of exercise and immediate client consultation with a physician, physical therapist, or other health care provider.
The prone I exercise can be performed on either a matted floor, (treatment) plynth table, or a multipurpose training bench. Plynth tables typically enable clients to place their faces within a cutout hole, which facilitates breathing and inline stabilization of the cervical and thoracic (neck and upper back) spines. A small pillow placed under the top of the pelvis and hips can provide additional alignment and support to the lower back. Clients also can place their foreheads on a small hand-rolled towel and place a small pillow under their waist and hips to achieve similar alignment if they are lying prone on the floor. The use of the floor or a plynth table provides the shoulder girdle with additional extrinsic support and reduces the distance in which the arms must be lifted from the starting position as compared with a multipurpose training bench (3,8). Exercise intensity can be increased by progressing from a supportive surface like the floor or treatment table to a multipurpose training bench, where the arm is raised and lifted through a greater range of motion. Clients should exhale during the lifting phase and inhale during the lowering phase of each exercise. External loading should never prevent clients from performing each exercise in a controlled manner. The prone I exercise performed on a plynth table and from a training bench with a stability ball and dumbbells appears in Video 1 (http://links.lww.com/FIT/A78) and Video 2 (http://links.lww.com/FIT/A79), respectively.
SHOULDER EXTENSION ("THE PRONE I")
The prone I can be performed with the glenohumeral (shoulder) joint in either a neutral (little finger pointed toward the ceiling) or external (thumbs towards the ceiling) position. (The starting and ending phase positions appear in Figure 2).
By concentric actions of the levator scapula, rhomboids, lower trapezius, and posterior deltoid, the scapulae are actively retracted (adducted), rotated downward and anteriorly tilted, and the upper arms are extended until they are parallel with one another and raised just above the hips and buttocks (1–4,7,8). The scapulae and arms are held in this position for a count of three, and clients should be advised not to allow the arms to hyperextend. Hyperextension of the arms at the shoulder joint can increase stress on the anterior shoulder joint (3,5,6). (The upward phase position on a plynth table and on a training bench and stability ball with dumbbells appears in Figures 3 and 4, respectively).
The arms and scapulae return to the starting position in a controlled manner by eccentric actions of the levator scapula, rhomboids, lower trapezius, and posterior deltoid (1–4,7,8).
Alternatively, the prone shoulder I (extension exercise can be performed in either the supine hook lying or standing positions with either resistance tubing, bands, or cables attached to a weighted cable column. These positions are an alternative for clients who are either uncomfortable or unable to tolerate lying in the prone position or who cannot tolerate getting up and down from a prone and/or horizontal position because of either pain or dizziness. The supine hook lying and standing position variations with resistance tubing externally secured appear in Figures 5 and 6 and in Videos 3 (http://links.lww.com/FIT/A80) and 4 (http://links.lww.com/FIT/A81), respectively.
The prone shoulder exercise series (T-Y-I-W) is a routine intended to improve scapulothoracic and glenohumeral joint muscle function and shoulder girdle stability. Exercises can be performed without external loading in clients who are either unaccustomed to doing them or are deconditioned. External resistance can be added in the form of dumbbells or cuff weights as tolerated by clients and as their strength and endurance improves.
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