Gregory J. Welk, PhD, is an assistant professor at Iowa State University in the area of physical activity and health promotion. He is an extensively published author and researcher in the field of physical activity assessments. His work with children and adults in both laboratory and field studies makes him uniquely qualified to address the challenges of collecting, processing, and interpreting data on physical activity. Dr. Welk previously worked at the Cooper Institute for Aerobics Research, where he studied the broad applications of public health and epidemiological research and gained a deep understanding of the importance of accurate assessments to advance research. Additionally, he is an active member, both regionally and nationally, of the American College of Sports Medicine; the Alliance for Health, Physical Education, Recreation and Dance; and the Society for Public Health Education. In his free time, Dr. Welk enjoys aerobic activities such as running, biking, cross-country skiing, and swimming, as well as golf and hiking. He makes his home in Ames, Iowa, with his wife, Karen, and their four children.