Plank to Pike Begin in plank position with two towels under the balls of your feet. Slowly bend both knees in toward the chest while keeping the arms straight, shoulders over the wrists, and maintaining a flat, tabletop back. After doing 10 reps, draw both knees to the right foot for five reps and then to the left foot for five. Repeat this 20-rep sequence two more times. Image Source: POPSUGAR Studios