Leisure-Time Physical Activity: Operationally Defined as Time, Work, and Intensity

Abstract

This study was designed to examine whether different determinants exist for expressing leisure-time physical activity (LTPA). LTPA was operationalized to represent time, work, and intensity to determine whether these variables measure the same construct. The theoretical model chosen to investigate LTPA was the theory of planned behavior. Rating scales assessed the perceived control (PC) and the intention to engage in LTPA (Int) among 129 high school girls. Using a compendium of physical activities with MET values, LTPA was assessed with a 21-day physical activity diary. LTPA behavior was operationally defined as duration in minutes (PA-time), work in total METs × minutes (PA-work), and average intensity per minute (PA-mean intensity). Pearson correlations, reliability analyses for rating scales, and hierarchical multiple regression procedures were used. Correlational analyses showed a strong relationship between PA-time and PA-work (r = .89, p < .001). PA-mean intensity was significantly related to PA-time (r = .36, p < .001) and PA-work (r = .53, p < .001). The total explained variability for the predictor variables of Int, PC, and the interaction of Int × PC was 9.8%, 18.0%, and 13.1% for the criterion variables of PA-time, PA-work, and PA-mean intensity, respectively. In conclusion, it appears that PA-time and PA-work are measuring the same construct, whereas PA-mean intensity measures possibly a different construct. Within the framework of the theory of planned behavior, the three LTPA determinants explicated substantially different amounts of variance explained with PA-work, predicted better by theory expectations.