The purpose of this study was to assess the validity of the System for Observing Fitness Instruction Time (SOFIT) for measuring physical activity of elementary and middle school children. Students (N = 173,92 boys and 81 girls) from Grades 1–8 completed a standardized protocol that included lying, sitting, standing, walking, running, curl-ups, and push-ups. Heart rates were used as a criterion for concurrent validity. The results confirm the validity of the physical activity codes of SOFIT for elementary and middle school children. Activity Categories 2–5 indicate different levels of energy expenditure, whereas Categories 1 (lying) and 2 (sitting) refer to the same energy expenditure level. The common distinction between SOFIT Levels 4 and 5 as MVPA (moderate to vigorous physical activity) and SOFIT Levels 1 to 3 as non-MVPA is valid. Curl-ups and push-ups should be coded as MVPA.
P. Rowe is with the Department of Sport and Movement Science at the Katholieke Universiteit Leuven, Tervuurse Vest 101, B 3001 Leuven, Belgium. J.M. Schuldheisz and H. van der Mars are with the Department of Exercise and Sport Science at Oregon State University, Corvallis, OR 97331.