Sit on a stability ball and roll back until you are stabilized on the upper part of your back. Raise the dumbbells over your head. While keeping your upper arms still, lower the dumbbells behind your head by hinging at the elbow joint. Once your forearms are parallel to the floor, return your arms back up to an overhead extension.
We love these adjustable dumbbells from Rep Fitness. They take up very little space and are also very durable compared to other adjustable dumbbells on the market.