This works your lower back, legs, glutes, and core. Lie on your back, arms at your sides, palms down, knees bent, and your heels pulled up close to your rear. Press your hips up until your thighs are parallel to the floor, and bring your hands together beneath you. Think about pushing your knees forward and pulling your pubic bone toward your bellybutton. Lift your chin slightly, slide your shoulder blades down, and widen your collarbones. Hold 30 seconds to 1 minute, then slowly roll your hips back down to the floor.