Physical activity, sedentary behavior, and perceived stress among adults : an application of the theory of planned behavior.

Background: Young and middle-aged adults engage in low levels of physical activity, high levels of sedentary behavior, and experience high levels of stress. Examining physical activity and sedentary behavior through the theory of planned behavior framework may provide useful insight to help address health issues in the population. The objective of this study was to evaluate the predictive value of the theory of planned behavior in explaining physical activity and sedentary behavior in young and middle-aged U.S. adults. Specifically, relationships between objectively measured physical activity and sedentary behavior over a 6-week period were examined using socio-demographic characteristics and theory of planned behavior constructs. A secondary objective was to measure stress dynamically and examine the relationship between stress and physical activity, and stress and sedentary behavior, over the same 6-week period. Methods: Participants (n=45, mean age=31 years, 70% female, 83% White) completed surveys that included sociodemographic information, theory of planned behavior constructs, and a weekly stress inventory. Participants also wore an activity monitor (i.e., Actigraph accelerometer or SenseWear Armband) for 6 weeks and completed the weekly stress inventory once weekly throughout the 6-week study period. Two longitudinal models were estimated to determine the relationship between TPB constructs, relevant socio-demographic characteristics, and perceived stress with sedentary behavior and physical activity over the 6-week study period. Results: Model fit indices supported the theory of planned behavior constructs in explaining physical activity and sedentary behavior. Model fit indices also supported a relationship between greater stress and less time spent being sedentary, but did not support a relationship between physical activity and stress in this sample. Conclusions: Results cautiously continue to support the use of the theory of planned behavior to explain physical activity and sedentary behaviors, though the constructs in this study explained less variance in intention and behavior when compared to previous research. More research should be conducted to understand the relationships between stress and physical activity, and stress and sedentary behavior. Researchers and practitioners should address physical activity, sedentariness, and stress in efforts to improve the health status of young and middle-aged adults.