The benefit: Placing one foot in front of you on a bench forces your hip and core muscles to work harder in order to keep your body stable. That way, you engage more muscles and burn more calories than you would if you did the exercise in a regular standing position.
How to do it: Grab a pair of dumbbells and place one foot in front of you on a bench or step that's just higher than knee level. Let the dumbbells hang at arm's length next to your sides, your palms facing forward [A]. Without moving your upper arms, bend your elbows and curl the dumbbells toward your shoulders [B]. Pause, then slowly lower the weights back to the start.