Abstract
Background
Few objective measurements of sedentary behavior exist. The relationship between sedentary time and body size, as measured by body mass index and waist circumference, has not been well explored in older adolescent university students.
Purpose
The dissertation had two aims. First, validate the inclinometry function of the ActiGraph GT3X+ to measure sedentary behavior in 18 to 20 year-old adolescents. Second, compare sedentary time to body mass index and waist circumference using week-long accelerometry data from older adolescent university students.
Methods
This descriptive study used the ActiGraph GT3X+ device for objective measurement of sedentary behavior. The study used quantitative methods and a convenience sample of 18 to 20 year-old older adolescent university students from a major mid-Atlantic university. Aim 1 was done in a laboratory-controlled environment, testing lying down, sitting, reading a book while seated, playing a video game, watching a video, seated conversation, using a stationary bike, standing, and walking. Aim 2 used week long accelerometry data in free-living conditions. Percent agreement to direct observation determined the accuracy of the inclinometer and multiple regression determined the strength of correlation between sedentary behavior time and body size.
Results & Discussion
For Aim 1, the inclinometer demonstrated poor validity, but the evidence did suggest that using the vector magnitude—a combination of the X, Y, and Z axes—and increasing the accepted threshold of 100 counts per minute to 150 counts per minute may be superior for measuring sedentary and active behaviors. In Aim 2, the sample had high sedentary time and high physical activity time, which is a deviation from the normal population at-large but is consistent with some research in similar age groups. Participants that identified more sedentary extracurricular activities also tended to have higher body sizes. Dissertation results have implications for nurses to address sedentary behavior with patients and health care workers. Nurses should educate and integrate research on sedentary behavior to improve patient outcomes. More research is needed to improve objective measurement of sedentary behavior in older adolescents. Additional analyses could be done using the existing data for future research.
