Lie with your back flat on an exercise mat, a short band just above your knees and a dumbbell resting across your hips. Place your feet hip width apart and your toes slightly turned out. Grip the dumbbell firmly in both hands. 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. Make sure to keep your heels pressed firmly into the ground and push your knees out against the band. When your hips reach full hip extension, squeeze your glutes and drive your knees out against the band. Reverse the motion and return to the start position, inhaling as you do so. Repeat for the required amount of time (or time).