Set up in a glute ham developer with your knees bent, hips extended, and torso upright. Straighten your legs while keeping your hips extended. Continue until your body is in a straight line and parallel to the floor, inhaling as you do so. Be sure not to lock out your knees so as to keep tension in your hamstrings. Pull yourself back to the starting position using your hamstrings, exhaling as you do so. Repeat.