Grip a pair of dumbbells firmly in both hands and stand with your feet slightly wider than shoulder width. With a slight bend in your knee, slowly hinge your hips back, inhaling as you do so and keeping a neutral spine. Keep your arms extended and the dumbbells close to your thighs throughout the movement. When your hips have hinged as much as possible, proceed to reverse the movement. Ideally you should not go further than 1-2 inches below the knee joint, otherwise you risk putting the load through your lower back and losing the tension in your hamstrings. Drive your hips forward with force, squeezing your glutes and hamstrings as you do so and exhaling. Pause for a count of one at the top, keeping your glutes tensed. Repeat.