Step 1
Starting Position: Sit on a properly-inflated stability ball (one that compresses approximately 6" under your body weight) with both feet firmly placed on the floor, hip-width or wider apart. Hold a dumbbell with both hands wrapped around the dumbbell handle. Stiffen your torso by contracting your abdominal/core muscles ("bracing"), and depress and retract your scapulae (pull your shoulders down and back), maintaining this position throughout the exercise. Your head and neck should be aligned with your spine.
Step 2
Upward Phase: Exhale and slowly press the dumbbell overhead, extending your elbows until your arms are vertical to the floor, elbows pointing forward but not completely locked. The dumbbell should be positioned directly over your head with your palms facing upwards and the dumbbell hanging vertically or angled slightly. Maintain your balance and avoid changing the position of your head, torso, upper arms, wrists and feet. Keep your feet pressed into the floor and your hips pressed up towards the ceiling to maintain stability throughout the entire movement.
Step 3
Downward Phase: Inhale and allow the weight to slowly bend your elbows, lowering the dumbbell behind your head in a controlled manner without moving your upper arms. Continue lowering the dumbbell until your elbows reach a 90 degree bend or until your upper arms begin to move backwards, but avoid making contact with the back of your head. Avoid changing the position in your head, torso, upper arms, wrists and feet.
Attempt to keep your upper arms vertical to the floor throughout the exercise and keep your elbows shoulder-width apart. Avoid hyperextension in your low back as you extend your elbows overhead.