Plank Jacks Begin in the plank position, with your shoulders over your wrists, your body in one straight line, and your feet together. Like the motion of jumping jacks, jump your legs wide apart, and then back together to complete a rep. Jump as quickly as you want, but keep your pelvis steady and don't let your booty rise toward the ceiling. Do as many plank jacks as you can in 30 seconds. Image Source: POPSUGAR Photography