He is currently U.S. Delegate and Secretary-General, World Council for Cardiovascular and Pulmonary Rehabilitation, plus a fellow and past president (1995-96) of the American Association of Cardiovascular and Pulmonary Rehabilitation. Humphrey is also a fellow of the American College of Sports Medicine, and served as associate editor of ACSM's Guidelines for Graded Exercise Testing and Prescription, fifth edition, and the recently published ACSM's Resources for Clinical Exercise Physiology.