By Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, H/FS
The muscles that comprise the POS are the largest in the body. This subsystem plays a significant role in stabilizing the lumbar spine, sacroiliac joint (SIJ) and hip, as well as transferring force between lower and upper extremities. The POS plays an active role in all pulling and rotational movement patterns (especially turning out), multi-segmental extension (with less lumbar extension - excessive lordosis), and eccentrically decelerates spinal flexion and rotation, as well as hip flexion, adduction and internal rotation (knees bow in and excessive forward lean). The POS is the functional antagonist of the Anterior Oblique Subsystem (AOS).