Anatomy

• Trapezius


  • Large muscle with descending, transverse, and ascending portions
  • Functions to elevate the scapula, extend the neck, and retract the scapula
• Infraspinatus


  Muscle that helps laterally rotate or externally rotate the shoulder joint
• Teres minor


  Muscle that helps laterally rotate or externally rotate the shoulder joint
• Teres major


  Muscle that extends the arm at the shoulder joint, adducts at the shoulder joint, and medially rotates the shoulder
• Latissimus dorsi


  Large muscle that extends the arm at the shoulder joint, adducts at the shoulder joint, and medially rotates the shoulder
• Teres major and latissimus dorsi


  Synergist muscles that perform the same shoulder joint actions
• Infraspinatus and teres minor

  Synergist muscles that perform lateral/external rotation of the shoulder
• Teres major and latissimus dorsi


  Antagonist muscles to infraspinatus and teres minor for shoulder rotation
• Rotator cuff muscles


  Supraspinatus, infraspinatus, teres minor, subscapularis
• Rhomboids

  Muscles that retract the scapula
• Erector spinae


  Muscles that extend the vertebral column and neck (spinalis, longissimus, iliocostalis)
• Erector spinae


  Antagonist muscles to abdominal wall muscles for vertebral column flexion/extension
• Quadratus lumborum


  Muscle that extends the lower back and fixes the ribs from below