Start lying on the ground with a foot in each cradle, your body facing away from the anchor point. Raise yourself into a plank position, hands under shoulders, strong core, glutes engaged. Hold this position for five seconds. At the end of the five seconds, pull knees in unison toward your chest (like you’re doing a crunch), then back out to plank position. Next, move your knees at an angle toward your right elbow, then back out to plank position. Lastly, move your knees at an angle toward your left elbow, then out to plank position. Repeat this sequence 10 times.