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 on your back holding a kettlebell in both hands over your chest and both legs raised to 90 degrees. Step 2 Lower one leg down to the floor and keep the kettlebell steady over your chest. Step 3 Raise your leg back up just before your heel touches the floor and repeat on the other side.