Latissimus Dorsi (Lats)
The back muscle group with the most mass is the latissimus dorsi or “lats.” These muscles connect to the back of your upper arms and extend along your spine from the mid to lower back.
The primary role of the lats is to pull your arm down and backward around the shoulder joint. To effectively target all parts of your lats, it’s essential to incorporate a variety of rowing and pulling movements.
Upper Back Muscles
Several smaller muscles on your upper back are connected to your shoulder blade. These muscles include the rhomboid, teres major, teres minor, and infraspinatus.
Functionally, the upper back muscles work with the lats to move your extremities around the shoulder joint. But they also stabilize and control the movement of the scapula during back exercises.
The trapezius or traps are a large diamond shape muscle connecting your neck, shoulders, and upper back. And you can think of the trap muscles as having an upper and lower part.
The lower traps get used extensively during rowing or pulling back exercises. At the same time, the upper traps’ primary function is elevating the shoulders during exercises like deadlifts or shrugs.