Stand tall atop an aerobic step (or equivalent), with your body parallel with the step. In one explosive movement, push through your feet and jump them either side of the aerobic step. Make a soft landing by bending your knees as your feet touch down. As you do so drive your hips back and down into a squat position. Keeping your core braced, chest lifted and a neutral spine. Reverse the movement by pushing through your feet and jumping them together so you come to a standing position again atop the aerobic step. Repeat the movement for the required number of reps (or time).