Starting Position: Stand in a split-stance position holding a dumbbell with both hands and wrap both hands 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.
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.
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. Be sure to avoid making contact with the back of your head. Also, avoid changing the position in your head, torso, upper arms, wrists and feet.