MUSCLES ENGAGED Abdominals The abdominal muscles (abs) provide movement and support to your core area. The deeper and closer to the spine the particular abdominal muscle is, the more effect over body posture it will have, and this often contributes significantly to a healthy back. Exercise Instructions Step 1 Start in a push-up plank position with your hands under your shoulders, your back flat and your feet together. Step 2 With both feet leaving the floor at the same time, jump out until your feet are slightly wider than shoulder width. Make sure to keep your back flat and your butt down. Step 3 Jump back to the starting position, once and again making sure both feet leave the floor and land back together at the same time.