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 plank position on your forearms and toes and your feet together. Step 2 Keep your back flat and core engaged as you open up and perform light toe taps with both legs. Step 3 Complete the recommended number of reps or amount of time or until you can no longer maintain the planks position.