The anterior oblique system (Figure 2.16) is similar to the POS in that it also functions in a transverse plane orientation, mostly in the anterior portion of the body. The prime contributors are the internal and external oblique muscles, the adductor complex, and hip external rotators. Electromyography of these AOS muscles show that they aid in pelvic stability and rotation as well as contributing to leg swing. The AOS is also a factor in the stabilization of the sacroiliac joint.54 During walking, the pelvis rotates in the transverse plane in order to create a swinging motion for the legs. The POS (posteriorly) and the AOS (anteriorly) contribute to this rotation. Knowing the fiber arrangements of the muscles involved (latissimus dorsi, gluteus maximus, internal and external obliques, adductors, and hip rotators) emphasizes this point. The AOS is also necessary for functional activities involving the trunk, upper and lower extremities. The obliques, in concert with the adductor complex, not only produce rotational and flexion movements, but are also instrumental in stabilizing the LPHC.
