Step 1: Begin in a plank position with your shoulders over your wrists, your feet together, and your body in a straight line. Step 2: Pull your right knee under your belly to touch your left elbow, then release back to start position. Step 3: Now pull your left knee under your belly to touch your right elbow, then release back to start position. Continue for the desired number of reps. Keep abs tight and keep the body in control.