Skip the basic core workout and try this short plank challenge that strings together a bunch of plank variations including plank shoulder taps, plank jacks, and up down planks. Created by certified fitness trainer James Stirling, known as London Fitness Guy, I've never seen such a fast-paced, fun fitness challenge that's so perfectly set to music. I can't get over how impressive this sequence is, even if he makes it look easy! Give it a try and see if you can keep up!