Get into a plank position, making sure to distribute your weight evenly between your hands and your toes. Keep your hands shoulder-width apart, back flat, abs engaged, and head in alignment. Pull your right knee into your chest as far as you can. Switch legs, pulling one knee out and bringing the other knee in. Keep your hips down and repeat 4 reps. Now come back into plank. Lower your right elbow to the mat and then your left, coming into an elbow plank. Put your right hand on the mat and straighten your right elbow. Do the same on the left to return to a full plank. That’s 1 Rep.