CYBEX VR2 Owner's And Service Manual page 77

• Associated Muscles - The rhomboids and middle fibers of the trapezius are responsible for
scapular retraction. The posterior deltoid is an assistant mover for shoulder extension. The
long head of the triceps is also involved in shoulder extension, although change in its length
is limited when elbow flexion coincides with shoulder motion. The biceps, brachioradialis,
and brachialis are always involved in pulling movements as elbow flexion is required. The
degree of their individual involvement depends upon radioulnar joint position.
The Posterior Deltoid
• Horizontal Abduction - The posterior deltoid is responsible for horizontal abduction of the
shoulder joint. Due to the attachment of the rear deltoid on the scapula, the scapula must
remain stabilized during shoulder joint motion. If scapular movement occurs, the resistance
will move without change in the length of the rear delt, minimizing effectiveness. The teres
minor and infraspinatus are also prime movers for horizontal abduction.
• Range of Motion - Horizontal abduction is limited concentrically at approximately 10 - 20
degrees (posterior to the shoulder) and eccentrically at approximately 90 degrees of horizon-
tal adduction (arms to the front) when the scapula remains retracted.
• Associated Muscles - The rhomboids and middle fibers of the trapezius are responsible for
stabilization of the scapula in retraction. The teres major and upper fibers of the latissimus
dorsi are assistant movers for horizontal abduction. The biceps, brachioradialis, and
brachialis are always involved in pulling movements as elbow flexion is required. The
degree of their individual involvement depends upon radioulnar joint position.
Exercise
Page 3-46
CYBEX VR2 Owner's Manual