This TRX movement is one of the best ways to isolate the rotational pulling power of your upper body.
Grab both straps in one hand, with the same-side elbow tucked in close to your body. Your other arm should be fully extended and pointing straight ahead. Lean back, extending the arm holding the straps, and let your other hand rotate back. Then pull yourself back up. The closer your feet are to the anchor point, the harder the move will become. Perform 8 reps on both sides.