I think this word best reflects the beginning of PRI concepts. The hamstring was the first muscle that I felt individuals needed to grasp and understand better for one to fully appreciate the lateralization that is taking place in our bodies using an orthopedic mentality. We have become products of our professional reading materials and if you cannot palpate a muscle, grasp onto the concept of its movement activity or have a good appreciation for origin, insertion, two joint mechanical activity, etc. the orthopedic mind will not allow one to integrate with families of muscles or polyarticular activity that result in chained limitation. This particular illustration is the beginning of that conceptual, philosophical approach to looking at the neural mechanical system that we all possess. The Supine 90-90 Hemibridge comes to mind when I think about the days I tried to facilitate this particular unilateral muscle. The results were magical, mysterious and fun to talk about but we’ve come a long way since then and the days of application of isotonic resistance to a muscle that is moving independently of speed, gravity, or position (i.e. Protonics) are no longer novelty to many of us. It’s important to understand the human body needs to be able to extend the sacrum, sphenoid and sternum without extending the appendicular structure or the back so that other PRI applications and algorithms can follow. When I look at “commencement” of establishing pelvic neutrality or system neutrality I think of this particular muscle, this particular illustration and my 30 years of studying and outlining the road for PRI instruction and teaching.