Subscapularis

Structure

This course describes the anatomy and integrated function of the subscapularis, which is 1 of 4 rotator cuff muscles (a.k.a. SITS muscles). Sometimes referred to as the anterior rotator cuff, the subscapularis originates from a depression that covers the majority of the anterior surface of the scapula (shoulder blade), known as the subscapular fossa. The subscapularis courses distally into the subscapularis tendon which inserts into the the superior and medial aspect of the lesser tubercle of the humerus and capsule of the glenohumeral (shoulder) joint. The subscapularis occupies its own fascial compartment, covered by a fascial sheath that may be a continuation of the axillary fascia and serratus anterior fascia by coursing medially, investing in the medial border of the scapula, and then folding back over itself covering the subscapularis. Research suggests that the subscapularis is a relatively large upper body muscle, contributing to approximately 6.6% of the total upper body muscle mass (for comparison, the pectoralis major contributes approximately 10%), and the subscapularis is the largest rotator cuff muscle (the infraspinatus is the 2nd largest rotator cuff muscle). Additionally, research suggests that the subscapularis is composed of only about 20 - 40% type I muscle fiber (4, 5).

Function:

The subscapularis muscle crosses the shoulder (glenohumeral) joint and contributes to internal rotation, adduction, and shoulder stabilization. This course also describes the role of the subscapularis on shoulder (glenohumeral) arthrokinematics, fascial integration, subsystem integration, and postural dysfunction. For example, the subscapularis may act synergistically with the latissimus dorsi, pectoralis major, and teres major to contribute to internal rotation and inferior glide of the humeral head in the glenoid fossa. If these actions occur excessively due to muscle over-activity, they may be a component of the sign "Arms Fall " during an Overhead Squat Assessment , and postural dysfunction (e.g. movement impairment) of the upper body.

Practical Application:

Sports medicine professionals (personal trainers, fitness instructors, physical therapists, massage therapists, chiropractors, occupational therapists, athletic trainers, etc.) must be aware of the integrated function of the subscapularis for detailed assessment and analysis of human movement, and the development of sophisticated exercise programs and therapeutic (rehabilitation) interventions. For example, altered activity and length of the subscapularis may contribute to rotator cuff injury, rotator cuff tears, shoulder pain, shoulder conditions, shoulder impingement syndrome (SIS), biceps tendon impingement and the resulting weakness and pain during motion such as external rotation and internal rotation. Altered subscapularis activity may also result in a reduction in infraspinatus and teres minor activity, resulting in a significant reduction in upper body speed, agility, and strength, and a reduction in the effectiveness of resistance training intended to improve upper body strength and hypertrophy (bodybuilding). Deeper knowledge of subscapularis anatomy is essential for optimal assessment, intervention selection, and building a repertoire of subscapularis specific techniques.

Sample Intervention: Loss of Shoulder Range of Motion

• Client/Patient History: History of shoulder pain
• Overhead Squat Assessment:
  • Arms Fall
• Goniometry:
  • Shoulder External Rotation in Supine: < 90°
  • Shoulder Flexion (with Scapular Motion) : <180°
• Manual Muscle Testing :
  • Shoulder External Rotator: Weak

Sample Self-administered Intervention

• Release
  • Subscapularis Static Release
  • Latissimus Dorsi Static Release
• Mobilization or Manipulation
  • Shoulder Mobilization
• Lengthening
  • Subscapularis (and Pectoralis Major and Minor) Static Stretch
• Activation
  • Shoulder External Rotation Isolated Activation
  • Serratus Anterior Isolated Activation
  • Standing Cobras (Trapezius Activation)
• Reactive Activation
  • Trapezius Reactive Activation
• Integration
  • Squat to Row (Posterior Oblique Subsystem)

Additional Courses and Techniques:

Brookbush Institute’s most recommended techniques for the Subscapularis (see videos below):

• Introduction to Functional Anatomy: Lesson 9: Rotator Cuff
• Self-administered Release: Subscapularis Static Release
• Manual Release: Subscapularis Static Manual Release
• Static Stretch: Subscapularis (and Pectoralis Major and Minor) Static Stretch
• Dynamic Stretch: Dynamic Pec (Pectoralis Major and Minor) Subscapularis Stretch
• Isolated Activation: Subscapularis Isolated Activation

Caption: The subscapularis muscle as part of the rotator cuff