The largest muscle in the back is scientifically known as the latissimus dorsi. You might see it referred to as the "lats" or "wings." The lats are used any time you pull something. For example, when you open a fridge or a car door, you are primarily using your lat muscles. The lat pulldown with resistance tubing is a great way to target the back muscles.
This execise can be done on the floor, chair, bench, ball, etc. First, anchor the resistance tubing up high. From a seated position, grasp the tubing handles and fully extend your arms over your head. Pull the tubing down to your neck/chest area. Slowly return to the starting position and repeat the movement. You should exhale as you pull the tubing downward.
From a seated position, grasp tubing with arms fully extended.
Pull tubing to neck/chest area. Exhale.
Slowly return to the starting position. Repeat.