Tim McComsey and Marzia Prince, fitness friends, trainers, and fantastic examples of the buddy system, combine their exercise skills once more to bring us a ladder hop partner plank. This time you don't want to have too much fun and distract yourself or you may end up stomping on your partner. One of you will get down and plank for 30 seconds while the other hops over you repeatedly. Then switch. That's all there is to it, but don't let the simplicity of this workout fool you. You will be toning your core, burning fat, building your legs, and getting your heart rate up quickly.