Sit on an exercise ball with a dumbbell in one hand. Walk your feet forward and roll your body down until your head, neck, and upper back are supported on the ball. Hold the dumbbell with your palm facing inward and your elbow bent at a 90-degree angle. Press the dumbbell up towards the ceiling, straightening your arm. Lower the dumbbell back down to the starting position. Repeat for the desired number of repetitions, then switch arms.
GIF