Mary Yoke has more than 30 years' experience teaching and training group exercise leaders. She has frequently served as a fitness video consultant and reviewer for Shape, Consumer Reports and Good Housekeeping. She has also worked in the areas of cardiac rehab, physiotherapy and corporate fitness and health promotion. A fellow of the American College of Sports Medicine (ACSM), Yoke is an associate research editor for ACSM's Health and Fitness Journal. Yoke has also coauthored all the previous editions of Methods of Group Exercise Instruction. Carol Armbruster is a senior lecturer in the department of kinesiology at Indiana University. During her 35 years of teaching college students and training fitness lecturers, Armbruster has served on the ACSM and American Council on Exercise credentialing committees. She enjoys combining her interests of teaching, community engagement and translational research. Armbruster is a senior editor for Translational Journal of the American College of Sports Medicine. She is specifically interested in functional movement, worksite wellness outcomes and safe and effective movement instruction.