Starting Position: Sit on the stability ball holding each dumbbell with your thumbs wrapped around the handles and your feet flat on the floor. Slowly begin walking your feet forward as you tuck your tail under, lowering your spine onto the ball as you walk your feet away from the ball until your head, shoulders and upper back are resting on the ball. Feet should be parallel and shoulder width apart. Knees are bent to about 90 degrees with your thighs and torso at or nearly parallel to the floor. Distribute your weight evenly through your feet.
Pull your shoulders down and back until you feel your shoulder blades hugging the ball. Position the dumbbells near your chest and armpits with your palms facing one another. Keep the wrist in a neutral position (straight, not bent).
Exhale, engage your abdominal/core muscles ("bracing") to stabilize your spine. Slowly press the dumbbells upward to a position directly above your chest. Arms should be shoulder-width apart or closer, with your elbows straight but not locked. Throughout the movement remember to keep your feet pressed into the ground and the hips pushed up towards the ceiling. This will create stability for your body during the movement.
Downward Phase: Inhale and slowly lower the dumbbells in a wide arc until the dumbbells are level with or near the height of your chest. Try to keep the dumbbells parallel with each other, a very slight bend in the elbows and wrists in neutral position (straight, not bent). Your head, shoulders and upper back should be resting on the ball, and your torso and thighs should be parallel with the floor at all times.
Upward Phase: Return the dumbbells toward the ceiling following the same soft arc pattern of the downward phase. Avoid the tendency to thrust your hips upwards and arch your back. Your torso and hips should remain strong and parallel with the floor throughout the exercise.