Set a bench flat and place your left knee on top of it, with your other leg straight and foot on the floor. Hold a dumbbell in your right hand, place your left hand on the bench directly under your shoulders and keep a neutral spine. Extend your right arm down towards the floor with your palm facing inwards. This is your start position. Keeping your spine neutral and your elbow close to your body, pull the dumbbell up and back towards your hips. Squeeze your back muscles as you do and exhale. Hold for a count of one before returning to the start position. Inhale as you do so. Repeat all the required reps (or time) on one arm before changing to the other.