It's a Plank Off! 31 Core Exercises for a Killer Beach Body

How much do you love planks? So much, right? You should, because this total-body toner does works all the muscles in your core (including the rectus abdominus, or the "six-pack muscles" you can see, transverse abdominus, and your internal and external obliques), your hips, your arms and shoulders, and your back. (It's The Secret Formula for a Flat Stomach.)

Yes, we know that holding a plank for more than 60 seconds can be tedious. Luckily, the plank is a classic fitness move with endless variations-and just when you think you've tried them all, there's the push-up, a moving version of the plank!

Because the plank is just that good for you, we teamed up with Fitness Magazine to bring you the ultimate plank challenge. Forget upping your time each day-in this exclusive, month-long challenge created by trainer Kira Stokes, you'll learn a new twist on the plank daily. Plus, at the end of each week, you'll put those moves together for a #FridayFlow that works your strength and endurance. Head over to fitnessmagazine.com/plankoff now to get instructions and start the challenge! By June 1, holding a plank for two whole minutes will be no sweat off your back. Just don't blame us for how your abs feel by the end (the burn is a good thing, trust us!).