Lie facedown with your legs extended shoulder-width apart behind you. Position the ball under your chest and rest your forearms on the floor, palms down, elbows close to your body. Bring your shoulder blades back and down, press your palms lightly on the floor, and slowly lift your head and chest as you lengthen your spine. Hold for two or three seconds and then return to the starting position. Make about 20 reps of this exercise.