There are many reasons why I like to give this exercise to shoulder and hip patients, one being joint compression. We are taught in our manual therapy classes that joint compression can be beneficial for healing; it also can help mobilize the posterior capsule. It also helps mimic the developmental patterns of weight bearing on the upper extremities, and thus is a critical part of rehabilitation. Additionally, the quad rock back exercise can be use to help normalize scapulohumeral movement patterns and avoid any compensatory activity. While performing the exercise, the movement can be completed by actively flexing the hips, instead of pushing away with the UE's. This allows the shoulder to move in a more normal pattern. Similarly, the exercise can help with unwanted hip musculature activity. By reversing the directions (instructing the patient to push with the hands and not actively flex the hips), the patient can decrease abnormal femoral head sliding and thus compete hip flexion less painfully.
The exercise can be used both for treating and assessing and low back dysfunctions, and not just because it is one of the more comfortable positions for low back pain. If you take your patient into quadruped and have them rock back, pay attention to the pelvis, hips, and low back. You may note a deviation to one side, suggesting increased muscle activity, stiffness, or movement patterns. Often you will note premature lumbar flexion compared to end-range hip flexion. This is secondary to all the sitting we do throughout the day - our lumbar spine becomes more flexible compared to the hip! By encouraging the patient to maintain a stable lumbar spine while rocking back (this can be done by placing a stick across the low back - if it falls off, we know there has been abnormal movement). This teaches our patients to isolate hip movement from back movement.
While I may not subscribe to all of Sahrmann's theories on movement impairment syndromes, especially in the acute phase, I do appreciate the focus she places on changing compensatory patterns with her exercises. Many of these patterns stem from abnormal postures or repetitive tasks that we perform throughout our daily lives. The rehab focuses on resisting any changes in movement that occur as a result. I have found that I get better results with incorporating repeated motions into my treatment, but I continued to use Sahrmann exercises to try and retrain movement afterwords.