There is no shortage of plank variations, and nearly all of them will work your core and arms, plus provide a quick burst of cardio, making it a great specific exercise to tackle as part of getting in shape. Find a baseline by starting in a standard high plank (on hand and toes) and using a stopwatch to see how long you can hold it. Commit to spending some time in plank every day, trying to add a couple seconds every day until you can hold it for one minute. Want to take it up a notch? Try a plank challenge.