Stand tall with the balls of your feet atop an aerobic step (or equivalent), your heels off the edge and holding a pair of dumbbells in each hand by your sides. Stand tall with your feet shoulder width apart, a braced core and flat back. Focusing the tension in your calf muscles, slowly raise yourself up on to the balls of your feet. Pause at the top of the movement, squeezing your calf muscles and slowly return to the starting position, feeling a stretch in your calves at the very bottom of the movement.