Exercise ball back extension with knees off ground

Place the stability ball on the ground and lie face down on top of it, with your hips resting on the ball and your feet against a wall for stability. Position your hands behind your head or crossed over your chest. Engage your core and slowly lift your upper body off the ball, extending your back until your body forms a straight line from your head to your heels. Pause for a moment at the top, then slowly lower your upper body back down to the starting position. Repeat for the desired number of repetitions.