Synergy has origins as a theological term describing the cooperation of human effort with divine will. In recent years the term has most often been used in association with systems theory. Systems theory, as applied to biology and the physical sciences, describes the interdependence of various parts of an organism, such as the human body. The human body, as a system, is comprised of a set of interrelated subsystems, including the brain, skeleton, muscles, and others. To fully understand the larger system, one must examine the subsystems and the interrelationships. Systems theory was one of the first management theories to explicitly state that changing one of the subsystems could have an impact on the total system. Synergy was developed as a measure of the effectiveness of the joint efforts of various subsystems. Discussions of synergy also figure in medical literature, such as in research that addresses how the effects of medication on individuals are magnified when combined with a special diet or exercise.