This document provides an overview of stretching and flexibility. It begins with the physiology behind stretching, including muscle composition and how stretching affects the body. It then discusses different types of flexibility, factors limiting flexibility like connective tissue and aging, and the relationship between strength and flexibility. The document also covers various stretching techniques like static, dynamic, ballistic, PNF stretching and provides guidelines for proper stretching form, warm-up, cool-down, duration and addressing pain or discomfort. Appendices include references and recommendations for stretching as well as progressions for achieving the splits.