MUSCLE SERIES #14: LESSER-KNOWN UPPER BACK MUSCLES — FUNCTION, FIBER TYPE, AND TRAINING STRATEGIES

INTRODUCTION TO THE SUPPORTING CAST  

Beyond the lats and traps lies a network of upper back muscles that quietly control scapular movement, shoulder positioning, and postural integrity. These muscles don’t get the spotlight, but they’re essential for joint health, pulling mechanics, and injury prevention. Whether retracting the scapula, stabilizing the neck, or resisting internal rotation, these structures keep the upper body aligned and resilient.

KEY MUSCLES AND STRUCTURE  

This group includes:

• Rhomboid major and minor — originate from the spine and insert on the medial border of the scapula; responsible for scapular retraction and downward rotation  
• Levator scapulae — runs from the cervical spine to the superior angle of the scapula; elevates the scapula and assists in neck stabilization  
• Posterior deltoid — originates from the scapular spine and inserts on the humerus; responsible for shoulder extension and horizontal abduction  
• Teres major — originates from the inferior angle of the scapula and inserts on the humerus; assists in shoulder extension and internal rotation  
• Infraspinatus — part of the rotator cuff, responsible for external rotation and posterior shoulder stability  
• Teres minor — originates from the lateral border of the scapula and inserts on the greater tubercle of the humerus; responsible for external rotation and glenohumeral joint stabilization

Together, these muscles form a layered support system that controls scapular rhythm, reinforces shoulder mechanics, and protects against overuse injuries.

FUNCTIONAL ROLE IN MOVEMENT AND STABILITY  

These muscles are responsible for scapular retraction, elevation, rotation, and shoulder extension. They stabilize the shoulder girdle during pulling, pressing, and overhead movement. In compound lifts like rows, face pulls, and overhead carries, they act as dynamic stabilizers. The teres minor and infraspinatus play a critical role in resisting internal rotation and maintaining joint integrity during pressing and overhead work. Collectively, these muscles support posture, neck alignment, and rotator cuff resilience.

DOMINANT MUSCLE FIBER TYPES  

This group contains a mix of fiber types, with a bias toward endurance and control:

• Rhomboids and levator scapulae: predominantly Type I (slow-twitch) fibers for postural control and sustained contraction  
• Posterior deltoid and teres major: mixed profile with Type IIa (fast oxidative) fibers for moderate force and fatigue resistance  
• Infraspinatus and teres minor: high Type I content for joint stability and fine motor control

This fiber distribution makes these muscles responsive to high-rep, time-under-tension work and isometric holds, with occasional heavier loading for strength development.

BEST EXERCISES TO TARGET THESE MUSCLES  

To train these muscles effectively, exercises should emphasize scapular control, shoulder extension, and external rotation. Here are five foundational movements:

• Face pulls — activate rhomboids, posterior delts, and rotator cuff  
• Chest-supported reverse flyes — isolate scapular retractors with minimal momentum  
• Band pull-aparts — reinforce scapular rhythm and endurance  
• Cable external rotations — target infraspinatus and teres minor  
• Overhead carries — build postural endurance and scapular stability

These exercises can be rotated across training blocks to develop strength, hypertrophy, and joint integrity.

TRAINING FOR HYPERTROPHY VS. STRENGTH  

For hypertrophy, these muscles respond well to moderate loads in the 12 to 20 rep range, with controlled eccentrics and full range of motion. Isolation movements like reverse flyes and band work should be emphasized, and training frequency can range from two to four sessions per week. Isometric holds and tempo work help reinforce endurance and scapular control.

For strength, heavier loads in the 6 to 12 rep range are more effective, especially when using compound lifts like rows and overhead carries. These sessions should be spaced out to allow full recovery, with longer rest intervals to preserve force output. Rotator cuff work, especially for the teres minor and infraspinatus, should remain low-load and high-frequency to protect joint integrity.

COMMON WEAKNESSES AND INJURY RISKS  

Weak or undertrained scapular stabilizers can lead to poor posture, shoulder impingement, and neck strain. Imbalances between internal and external rotators often result in poor pressing mechanics and increased injury risk. The teres minor, in particular, is often neglected, leading to instability and anterior glide of the humeral head. To prevent injury, include thoracic mobility work, vary movement planes, and maintain balanced development across the upper back.

INTEGRATION INTO TRAINING PROGRAMS  

Upper back accessory work should be integrated into push–pull or full-body routines two to four times per week. Combine compound and isolation movements, and include both dynamic and isometric loading. For athletes, integrate scapular rhythm drills, rotator cuff conditioning, and postural endurance work to reinforce performance and durability.

CONCLUSION  

The rhomboids, levator scapulae, posterior deltoid, teres major, infraspinatus, and teres minor are the unsung heroes of upper back function. Their fiber composition and anatomical structure demand thoughtful programming, from endurance work to joint-specific control. By targeting these muscles with precision and balancing volume with recovery, lifters and athletes can build a resilient upper back that supports performance and resists injury.