This dissertation examines the social and scientific factors which fostered the inclusion of strength training as an adjunct to sport preparation programs. It utilizes Thomas Kuhn's theory of "paradigm shift," outlined in his 1962 treatise The Structure of Scientific Revolutions, to describe how strength training went from an activity perceived as harmful and deleterious to sport, to one which is now considered an indispensable component of optimal performance. In the late-nineteenth and early-twentieth centuries physicians, physiologists, and physical educators theorized that the body operated under the constraints of fixed capacities. Increased demands by one component of the body necessarily robbed nourishment from other parts. Under this paradigm, increased muscular strain posed a risk to other organ systems and was advised against. Through a thorough exploration of the scientific literature, this work demonstrates the evolution of the understanding of physiology which precipitated the displacement of the old paradigm. In addition to scientific literature, popular magazines are also utilized because of their importance in the erosion of the old paradigm and in laying the groundwork for the acceptance of the current paradigm of strength training as an adjunct to athletic performance. Moreover, this work discusses the importance of the Second World War, the Cold War, and the Olympics in hastening the demise of the belief that strength training was physically and athletically harmful. The number of athletes training with weights in the United States dramatically increased in the 1950s and the pace accelerated through the 1960s. The endorsement of the new paradigm was cemented with the hiring of specialists in strength training who went on to create their own literature and sponsor their own research. Completion of the paradigm shift is evident in the contemporary ubiquity of weight training which is performed for nearly all sports, all age groups, year-round, often in highly specialized facilities and overseen by individuals certified as strength and conditioning or performance-enhancement specialists. / text