Progressive Angular Isometric Loading (PAILs) is verbiage coined by Dr. Andreo Spina, creator of Functional Anatomy Seminars (www.functionalanatomyseminars.com), to describe adding muscle contractions at progressively increasing ranges of motion in order to demonstrate to the nervous system that you do indeed have control of the new found range. This video demonstrates their use in order to improve hip mobility into a "split hinge" pattern.