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The Relationship Between Objectively Measured Sedentary Behavior and Physical Activity: Results from a Randomized Lifestyle Intervention

Lynette L. Craft, Northwestern University 
*Peter John D. De Chavez, Northwestern University 
Patty Freedson, University of Massachusetts 
Juned Siddique, Northwestern University 
Bonnie Spring, Northwestern University 

Keywords: sedentary behavior, physical activity, accelerometer, moderate-to-vigorous physical activity, mixed-effects,

Both sedentary behavior and physical activity have been shown to be independent predictors of cardiovascular disease, cancer, and diabetes mellitus. Less is known about the relationship between these two behaviors and whether increasing physical activity results in changes in sedentary behavior.

Objective: To investigate whether changes in physical activity over time result in changes in sedentary behavior and whether individuals compensate for increased physical activity by increasing sedentary behavior.

Methods: Our sample consists of five weeks of daily accelerometer data from the Make Better Choices study, a lifestyle intervention trial in which 204 participants were randomized to either increase physical activity or decrease sedentary behavior. We used mixed-effects regression models to investigate the effect of daily moderate-to-vigorous activity (MVPA) on daily sedentary behavior.

Results: Participants were mostly (77%) women with a mean (SD) age of 33 (11) years. They were either White (53%) or African American (23%) and 70% had at least a college degree. At baseline, mean (SD) BMI was 28 (7) kg/m2 and participants spent an average (SD) of 9.1 (10.3) hours per day engaged in sedentary behaviors. The median MVPA at baseline was 0 minutes per day (IQR: 0 – 14). On a given day over the course of the intervention, for each additional minute that participants increased their MVPA above their 5-week average, sedentary behavior decreased by 0.6 minutes per day (95% CI: -0.7, -0.4; p<.001).