Subscapularis muscle activity during selected rehabilitation exercises

Area of Science:

• Biomechanics
• Human Anatomy
• Exercise Physiology

Background:

• The subscapularis muscle, a key rotator cuff component, has independently innervated and activated upper and lower portions.
• Understanding these functional differences is crucial for targeted therapeutic interventions.

Purpose of the Study:

• To investigate the differential activation of the upper and lower subscapularis muscle portions during various shoulder-strengthening exercises.
• To identify exercises that selectively or effectively activate both functional parts of the subscapularis muscle.

Main Methods:

• A controlled laboratory study involving fifteen healthy subjects.
• Electromyographic data were collected from multiple shoulder muscles, including the upper and lower subscapularis, during seven different exercises.

Main Results:

• Upper subscapularis activity generally exceeded lower subscapularis activity across most exercises.
• The push-up plus and diagonal exercises demonstrated the most significant activation of both upper and lower subscapularis portions.
• Internal rotation at 0 degrees of humeral abduction showed different activation patterns compared to other exercises.

Conclusions:

• Humeral abduction angle significantly influences selective activation of the upper versus lower subscapularis muscle, supporting distinct exercise progressions.
• Push-up plus and diagonal exercises are more effective than traditional internal rotation exercises for activating both subscapularis portions.
• The functional independence of subscapularis portions necessitates tailored training and rehabilitation protocols for rotator cuff injuries.