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. Equipment Used Pull Up Bar A pull-up bar is a straight steel bar that mounts on a wall, door frame, squat rack or cable machine. It is one of oldest and most effective strength tools and is used to target the latissimus dorsi muscle (lats) along with the rhomboids, shoulders and biceps. Exercise Instructions Step 1 Start hanging on a pull-up bar with your grip about shoulder width Step 2 Pull your knees up as high as you can and hold. Step 3 Hold your knees up until you can't keep them above your hips.