1. Muscles Acting on Shoulder Comparative Analysis: Strongest to Weakest

2. A. Adduction 1. Pectoralis Major 2. (long head) Triceps 3. Teres Major
1. Pectoralis Major
2. (long head) Triceps
3. Teres Major
4. Latissimus Dorsi
5. (short head) Biceps
6. Clavicular and spinal parts of deltoid
Adduction notes: Trail Guide also lists
Teres minor and coracobrachialis
strongest to weakest: red, blue, yellow, orange, green, brown

3. B. Abduction 1. Deltoid 2. Supraspinatus (long head) biceps *
strongest to weakest: red, blue, yellow, orange, green, brown
1. Deltoid
2. Supraspinatus
(long head)
biceps *
* Trail Guide does NOT list (long head) biceps

4. C. Elevation: a continuation of abduction above 90 degrees --- requires upward rotation of scapula
strongest to weakest: red, blue, yellow
1. Serratus Anterior
2. Trapezius (in the transition from abduction to elevation, the trapezius supports serratus anterior)
Before elevation… need to abduct:
1. Deltoid
2. Supraspinatus
3. (long head) biceps

5. What drives upward rotation of the scapula?
During the early phase of upward rotation, the scapula and the clavicle move together
Serratus anterior (SA) and upper trapezius (UT) produce upward rotation moments
Once tension in the costoclavicular ligament prevents further elevation of the clavicle at the sternoclavicular joint, the axis for scapular rotation moves to the acromioclavicular (AC) joint.
Serratus anterior (SA) and the lower trapezius (LT) produce upward rotation moments.

6. Anteversion = Flexion of the glenohumeral joint
1. Deltoid (anterior fibers)
2. Biceps Brachii
3. Pectoralis Major
4. Coracobrachialis
5. Serratus Anterior *
* Trail Guide does NOT list
Serratus Anterior

7. Retroversion = extension
1. Teres Major
2. Latissimus Dorsi
3. (long head) Triceps
4. Deltoid (posterior)
Trail Guide also lists:
Infraspinatus, Teres Minor, Pectoralis Major (lower)

8. Lateral Rotation
1. Infraspinatus
2. Teres Minor
3. Deltoid

9. Medial Rotation 1. Subscapularis 2. Pectoralis Major
2. Pectoralis Major
3. (long head) Biceps *
4. Deltoid (anterior)
5. Teres Major
6. Latissimus Dorsi
* Trail Guide does NOT list: (long head) Biceps