Sit on an upright bench that has a back support, holding a dumbbell in each hand with an overhand grip and with both feet firmly on the floor. Raise the dumbbells upto your shoulders, level with your ears, with the palms of your hands facing forwards and your elbows in line with your shoulders. This is the start position. As you exhale, push the dumbbell in your left hand up and directly over your head by extending your arm, all the while maintaining the same position with your right arm. Think about initiating the push from your elbows as opposed to your hands. Slowly return to the left arm start position, inhaling as you do so. Repeat for the same movement with the other arm. Keep alternating sides for the required number of reps (or time).