Double Hip Extension: Lie on your back and bend your knees so that your feet are flat on the floor. Slide your arms out to your sides at 45-degree angles, palms facing up. Tighten your core, then squeeze your glutes to lift your hips an inch off the floor. This is the starting position. Raise your hips toward the ceiling until your body forms a straight line from shoulders to knees. Pause, then lower to the starting position. That's one rep. Do 10.