- Rotator Cuff
- Internal Rotation
- Anterior Stability
- Posterior Stability
- Scapula (Anterior)
- Subscapularis Fossa
- Humerus (Proximal Anterior)
- Lesser Tubercle
See other rotator cuff muscles:
All heads of subscapularis have their largest internal rotation moment arm (approximately 2.5 cm) and torque generation at 0° abduction. As abduction angle increases, moment arms of inferior and middle heads stay relatively constant, while moment arm of superior head progressively decreases until it is about 1.3 cm at 60° shoulder abduction (Otis JC, et al. 1994). However, no significant difference in upper subscapularis activity was observed during shoulder internal rotation exercises at 0°, 45°, or 90° adduction (Kadaba MP, et al. 1992; Decker MJ, et al. 2003).
The literature is mixed and inconclusive as to what position to perform internal rotation exercises (0° versus 90° adduction). However, it is interesting to note greater assistance of other muscles (Pectoralis Major, Latissimus Dorsi, and Teres Major) when performing shoulder internal rotation exercises at 0° as opposed to 90° shoulder abduction (Decker MJ, et al. 2003).
Subscapularis also generates abduction torque during arm elevation, particularly superior head when shoulder is externally rotated (Otis JC, et al. 1994). Subscapularis has peak abductor moment arm of 1 cm at 0° abduction, with a gradual decrease to 0 cm at 60° abduction in neutral rotation (Liu J et al. 1997).