Published in 2002, SOPLAY was designed to obtain observational data on the number of students and their physical activity levels during play and leisure opportunities in a specific activity area. SOPLAY is based on momentary time sampling techniques in which systematic and periodic scans of individuals and contextual factors within pre-determined target areas are made. During a scan the activity of each individual is mechanically or electronically coded as Sedentary (lying down, sitting, or standing), Walking, or Very Active.
McKenzie, T.L., Marshall, S.J., Sallis, J.F., and Conway, T.L. (2000). Leisure-time physical activity in school environments: An observational study using SOPLAY. Preventive Medicine, 30 ,70-77.