This three-part text, which is concerned with human functions under stress of muscular activity, provides a basis for the study of physical fitness and athletic training. Part 1 reviews pertinent areas of basic physiology. Muscles, the nervous system, the heart, respiratory system, exercise metabolism, and the endocrine system are reviewed. Part 2 directly relates physiology to practice in physical education and discusses physical fitness, metabolism and weight control, prophylactic and therapeutic effects of exercise, electronyography in physiology of exercise, muscle soreness, and environment and age in relation to exercise. Part 3 relates the principles of physiology directly to the problems of the athletic coach and emphasizes areas of practical importance. Physiology of muscular strength, development of endurance, efficiency of muscular activity, speed, flexibility, warming-up, nutrition, special aids to athletic performance, and the female in athletics are discussed. The final chapter, entitled "The Unified Athlete: Monitoring Training Program," is a summary designed to encourage coaches to apply the principles of exercise physiology to their work on the athletic field. A bibliography is included at the end of each chapter. (PD)