ABSTRACT
Only about 12% to 22% of adults in the United States engage in leisure time physical activity at recommended levels, and, depending on the strictness of the definition used, 24% to 60% are sedentary (Caspersen, Merritt, & Stephens, 1994). Furthermore, once sedentary individuals become active, the mean dropout rate from supervised exercise programs reported around the world has remained at roughly 50% over the past 20 years (Dishman, 1988a, 1994a; Morgan, 1977). In addition, the 1990 participation rate objectives set by the U.S. Public Health Service for vigorous and frequent leisure time physical activity (Powell, Spain, Christenson, & Mollenkamp, 1986) were not met (CDC, 1991). The midcourse review (DHHS, 1993) of the physical activity goals outlined in Healthy People 2000, the U.S. health promotion and disease prevention objectives for the year 2000 (DHHS, 1991), suggests that they too will not be met.
