Exercise ball on the wall calf raise (tennis ball between knees)

Stand with your back against a wall and place an exercise ball between your lower back and the wall. Position your feet shoulder-width apart and slightly in front of you. Hold a dumbbell in each hand, with your arms extended by your sides. Place a tennis ball between your knees. Raise your heels off the ground, lifting your body up onto your toes. Pause for a moment at the top, then slowly lower your heels back down to the starting position. Repeat for the desired number of repetitions.