Arnold Shoulder Press

Step 1. Sit on a bench with your back supported. Hold a pair of dumbbells in front of your shoulders, palms facing you and elbows in front of your body.

Step 2. Press the dumbbells overhead while rotating your hands, so that your palms face forward at the top. Stop just before your elbows lock out.

Step 3. Reverse the movement under control: lower the dumbbells and turn your palms back towards you until you are in the starting position again.

Step 4. As shown here: https://www.youtube.com/watch?v=vj2w851ZHRM