Practitioners of occupational therapy in the early 1900s selected therapeutic activities with an intuitive understanding of their characteristics and operations. The term activity analysis and the methodology for breaking down and examining tasks scientifically, however, were borrowed from industry during World War I. Methods originally used in time and motion study of jobs were applied to vocational retraining and therapeutic crafts; later, they were applied to a broader range of activities. The most systematic early use of activity analysis was in occupational therapy for physical dysfunction, particularly in military hospitals. Development of the concept was gradual until the 1970s, when the delineation of theoretical frames of reference for practice led to important changes. Today, activity analysis is viewed as a multifaceted process that involves both generic and specific components.