Stand with an aerobic step (or equivalent) a small distance in front of you, whilst holding one kettlebell racked at shoulder height in your right arm and one kettlebell in your left hand with your arm extended by your side. Stand tall with your core braced and a flat back. Take a step forward onto the aerobic step with your right leg. This is your start position. Bend at the knee, slowly lowering your body until your front knee is bent at least 90 degrees, whilst your rear knee should be hovering just off the floor. Inhale as you do so. Keep your torso upright the entire time and look forward. Pause at the bottom of the movement, then extend your knee as you and return to the split stance start position. Repeat for the required number of reps (or time) on one side before changing to the other, ensuring you also swap the kettlebells' positions.