In 1964, at the beginning of my PhD studies at Southern Illinois University, I was first introduced to the theory and practice of proprioceptive neuro­ muscular facilitation (PNF). One specific application, reversal of antago­ nists, particularly intrigued me, and served as the focus of not only my dissertation, but also numerous research projects, presentations, and pub­ lications over the ensuing years, including the monograph Scientific Stretch­ ing for Sport (1973). This was the first publication to present a simplified. planar version of reversal of antagonists for enhancing flexibility. Although I was repeatedly encouraged by friends and colleagues to write a more extensive text, I knew that more laboratory research, methodologi­ cal fine-tuning, clinical information, and significant changes to the concep­ tual foundations, were needed before a truly meaningful book could be written. Throughout my 36 years at Dalhousie University. I have been fortunate to have had a number of excellent graduate students whose theses contrib­ uted much of this needed material. Their work has been published in numerous academic journals and is referenced throughout this text.