Professor Faulkner’s research focuses on age-related changes that occur in the structure and function of whole skeletal muscles, of motor units, and of single skeletal muscle fibers of selected mammals, specifically, humans, rats and mice. In each species, his group has investigated the changes that occur in motor unit number, size and function in specific limb muscles throughout the life span and of the effects of training programs on the age-related changes. Specific knock-outs of selected metabolic pathways in the muscles of mice have enabled investigations of the role of reactive oxygen species in the age-related changes.