These will aid in building muscles in your shoulders, especially the back of your shoulders, and also activate your back muscles.
You’ll also be actively engaging your core muscles to keep you balanced and steady on the stability ball as you perform the exercise
Performing the Exercise:
Place the dumbbells on either side of the stability ball, then stand in front of the ball.
Carefully lower yourself onto the stability ball such that your chest is supported by the dome of the ball. Extend your legs behind you so that your head, shoulders hips, knees and heels are aligned. Tuck your toes under to support your weight and the ball. Use the muscles in your abdomen and lower back to support your spine and hold you in position.
Allow your arms to dangle down over the sides of the stability ball and pick up the dumbbells.
Squeeze your shoulder blades back and down, and lift the dumbbells by pulling back the upper arms and bending your elbows. At the height of the movement, your elbows will be bent at 90 degrees and your upper arms will be lifted to form a straight line with your shoulders. Make sure that your wrists and forearms remain in line.
Slowly return the dumbbells to the start position, rest and repeat until you have completed your repetitions.
Throughout the exercise, make sure that you don’t arch your back. You should also be careful to keep your head in line with your spine. A good way to ensure this is to keep looking at the ground while performing the exercise.
Once you are comfortable with this exercise you can make it more challenging by alternating your arms, instead of raising them both at the same time.