System for Observing Play and Leisure Activity in Youth (SOPLAY)

Author of Tool: 

Thomas L. McKenzie, Ph.D.

Key references: 

1. McKenzie, T. L., Marshall, S. J., Sallis, J. F., & Conway, T. L. (2000). Leisure-time physical activity in school environments: An observational study using SOPLAY. Preventive Medicine, 30, 70-77.

2. McKenzie, T. L., Sallis, & Nader, P. R. (1991). SOFIT: System for observing fitness instruction time. Journal of Teaching in Physical Education, 11, 195-205.

3. Rowe, P.J., Schuldheisz, J.M., & van der Mars, H. (1997). Measuring physical activity in physical education: Validation of the SOFIT direct observation instrument for use with first to eighth grade students. Pediatric Exercise Science, 9(2), 136-149.

4. Sallis, J. F., Conway, T. L., Prochaska, J. J., McKenzie, T. L., Marshall, S. & Brown, M. (2001). School environments are associated with youth physical activity. American Journal of Public Health, 91, 618-620.

5. McKenzie, T. L. (2005, November). Systematic Observation: SOPLAY/SOPARC Introduction, Practice, and Assessment. (27 minute DVD). San Diego State University, San Diego, California. (T. McKenzie, author, producer, narrator; D. Graves, editor). Available from Active Living Research, San Diego State University, 3900 Fifth Avenue, Suite 310, San Diego, CA 92103 ( or the author.

Primary use / Purpose: 

SOPLAY was designed to obtain observational data on the number of students and their physical activity levels during play and leisure opportunities in a specified activity area.


The System for Observing Play and Leisure Activity in Youth (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. Separate scans are made for females and males, and simultaneous entries are also made for time of day, temperature, area accessibility, area usability, presence of supervision, presence and classification of organized activity, and equipment availability. Summary counts describe the number of males and females in any given setting and their activity levels. The instrument permits physical activity level comparisons to be made among different environments or within the same environment over different time periods. Energy expenditure rates (Kcal/kg/min) can also be calculated based on previously validated constants for each level of activity. (Excerpt from McKenzie, 2006, 'Description and Procedures Manual')


Although no field-based validity study of the SOPLAY measure has been conducted, validity of the activity codes used by SOPLAY have been established through heart rate monitoring (McKenzie et al., 1991; Rowe, Schuldheism, & van der Mars, 1997). These provide support for the initial construct validity of SOPLAY.



Digital Object Identifier (DOI):