Lie with your back flat on an exercise mat and a dumbbell resting on your lap. Place the balls of your feet together and let your knees fall out to the either side. Ensure the heels of your feet are fairly close to your glutes and that your pelvis is tucked forward (ensuring you have no arch in your back whilst lying down). Focusing the tension in your glutes, drive your hips up to full hip extension, exhaling as you do so. Pause for a count of one when your hips reach full hip extension, keeping the tension in your glutes and then return with control to the start position, inhaling as you do so. Repeat.