The American College of Sports Medicine (ACSM), founded in 1954, is the largest sports medicine and exercise science organization in the world. With more than 50,000 members and certified professionals worldwide, ACSM is dedicated to improving health through science, education, and medicine. ACSM members work in a range of medical specialties, allied health professions, and scientific disciplines. Members are committed to the diagnosis, treatment, and prevention of sport-related injuries and the advancement of the science of exercise. The ACSM promotes and integrates scientific research, education, and practical applications of sports medicine and exercise science to maintain and enhance physical performance, fitness, health, and quality of life. Timothy G. Lohman, PhD, is a professor emeritus at the University of Arizona and is widely considered a leading scientist in the field of body composition assessment. His research includes serving as principal investigator (PI) of both the TAAG (Trial of Activity for Adolescent Girls) study—a collaborative multicenter study focused on physical activity of adolescent girls—and the Bone Estrogen Strength Training (BEST) study. He was co-PI of the Pathways Study, a collaborative study (by the National Heart, Lung, and Blood Institute; four field centers; and a coordinating center) designed to prevent obesity in Native American children. Lohman served as a consultant to the Women’s Health Initiative (WHI) Vanguard Center and Health ABC study of long-term aging, and he was an advisor on youth fitness for the Cooper Institute. He previously served as the director of the Center for Physical Activity and Nutrition at the University of Arizona. He is a member of the American College of Sports Medicine. Lohman’s additional works, published by Human Kinetics, include his co-edited Human Body Composition, Second Edition; his authored monograph, “Advances in Body Composition Assessment”; and his co-edited Anthropometric Standardization Reference Manual. His research in body composition helped to establish the chemical immaturity of children using the multicomponent model. Laurie A. Milliken, PhD, FACSM, is an associate professor and former chair of the exercise and health sciences department at the University of Massachusetts at Boston. In the New England chapter of the American College of Sports Medicine (NEACSM), she has served as a state representative, an executive committee member, the Continuing Education Committee chair, and president, and she has been an active member since 1998. Nationally, she has served on the ACSM Research Awards Committee and is also an editorial board member of ACSM’s Health & Fitness Journal. She is currently a peer reviewer for leading scientific journals such as Medicine & Science in Sports & Exercise, the Journal of Applied Physiology, and the European Journal of Applied Physiology. She has been a member of ACSM since 1994 and has presented her research at many annual meetings. Her research interests include the regulation of body composition in response to exercise throughout the lifespan. She has received NIH funding for her work and is also a fellow of the American College of Sports Medicine.