Core reaches are a core exercise meant to strengthen the abdominal muscles. Begin by laying on your back, knees bent with your heels close to your butt. As you do the sit-up reach your hands between your legs until they pass the threshold of your calves, then lower back into the starting position. Do not use your hands in a rocking motion, but have them remain extended, palms facing the floor. The workout suggestion is 3 sets of 20 reps.