Set up in a glute ham developer with your knees bent, hips extended, and torso upright. Bracing your core and keeping a flat back, slowly lower towards the floor. All the while keeping your hips and knees in alignment, not bending at the waist and inhaling as you do so. Continue to lower until you can no longer control the descent. At this point pause, contract your hamstrings and pull yourself back to the starting position using your hamstrings, exhaling as you do so. Repeat.