3 SETS OF 10 REPS ON EACH LEG
Don’t rest just yet. Face away from the box and take a step forward. Now, prop a foot on top of it ( A). Bend your front leg until your back knee touches the floor, keeping your spine straight ( B). Hold for a second, then squeeze your glutes and drive yourself back up. Work both legs, then rest for 90 seconds before launching into your second set of step-ups.