Constant tension for a thick mid-back.
Keep your chest up and don't rock back, let your back do the pulling.
The seated cable row keeps tension on your mid back through the entire stroke, from the stretched reach at the front to the shoulder-blade squeeze at your stomach. That constant pull is the cable's edge over a barbell, which unloads the back at the bottom of every rep. Your biceps assist the pull, but with your chest up and your torso quiet, this is the volume machine for building back thickness.
Stay near upright with just a slight lean forward at the stretch. Rocking your torso back turns the row into a lower-back swing, if the handle only moves when your body does, the stack is too heavy.
The barbell row loads heavier but taxes your lower back holding the hinge. The cable row is supported, keeps tension constant, and lets you push sets harder with less fatigue. Most backs are built on both.
Let your shoulder blades glide forward for a full lat stretch, but keep your chest tall and spine long. Slumping your whole torso over isn't extra range, it's just lost position you have to fix mid-rep.
