Dumbbell one arm hammer press on exercise ball

Sit on an exercise ball with your feet flat on the ground and your back straight. Hold a dumbbell in one hand with your palm facing inwards and your elbow bent at a 90-degree angle. Place your other hand on your hip for stability. Press the dumbbell upwards, extending your arm fully. Pause for a moment at the top, then slowly lower the dumbbell back to the starting position. Repeat for the desired number of repetitions, then switch arms.