Grab the end of a bath or beach towel with each hand and roll it up as if you were ready snap it at someone in the locker room. Stand on the middle of the towel with your right foot, bend at the waist and right knee slightly, and straighten your left leg out behind you supporting yourself on the ball of your foot. With chest up, flatten your back so it forms a straight line from your heel to your head. With a firm grip on each end of the towel, pull as hard as you can toward your body, squeezing your shoulder blades together.
Maintain this isometric hold for 30 to 60 seconds, taking breaks as needed.