Duane V. Knudson, PhD, is a Regents’ and University Distinguished Professor in the department of health and human performance at Texas State University, where he teaches biomechanics. He earned his doctorate at the University of Wisconsin–Madison and has held tenured faculty positions at three universities. His research areas are in the biomechanics of tennis, stretching, qualitative movement diagnosis, and learning biomechanical concepts. Knudson has authored over 150 peer-reviewed articles, 22 chapters, and three books: Fundamentals of Biomechanics, Qualitative Diagnosis of Human Movement, and Biomechanical Principles of Tennis Technique. He has received numerous state, regional, national, and international awards for his research and leadership. Knudson has been elected fellow of four scholarly societies, including the prestigious National Academy of Kinesiology. He has served as department chair, associate dean, and president of the American Kinesiology Association and as president of the International Society of Biomechanics in Sports. Timothy A. Brusseau, PhD, is an associate professor and the chair of health and kinesiology at the University of Utah. He earned his PhD at Arizona State University and previously served on the faculty at the State University of New York at Brockport. Brusseau is a national expert on youth physical activity, physical activity measurement, and school-based multicomponent physical activity interventions. He has more than 145 peer-reviewed publications and has made more than 180 conference and invited presentations on topics related to youth physical activity. He is coauthor of Dynamic Physical Education for Secondary School Students and associate editor of Research Quarterly for Exercise and Sport. He has received numerous awards for his teaching and research. He is currently on the board of directors of the American Kinesiology Association and is a fellow in the American College of Sports Medicine.