Date of Award

12-2002

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Susan S. Sullivan

Second Committee Member

Richard A. Cook

Third Committee Member

Robert Lehnhard

Abstract

Physical activity is recorded in bone mineralization studies because physical activity increases bone mass and decreases the risk of osteoporosis. The purpose of this research was to validate a method of physical activity recording used in a longitudinal bone study of adolescent girls. The physical activity recording method was a combination of a diary and an interview-administered recall. The method was validated against an objective measure of physical activity. Twenty-four adolescent girls between the ages of 9.8 and 14.1 wore Stayhealthy RT3 Research Trackers (tri-axial accelerometers) arid recorded their activity for 24 hours on a diary form. The activity records were reviewed during telephone interviews the following day. The girls were asked to classifjl each period of activity into one of three categories: sitting ( 4 metabolic equivalent (MET)), low intensity (1-3 METs) and high intensity (>3 METs). Motion detected by the accelerometers was converted to METs and the average recorded METs were determined for each period of reported activity. The means of the recorded METs for the time periods when the subjects reported sitting, low intensity, and high intensity activities all fell within the pre-determined ranges. When 99% confidence intervals were constructed, the confidence interval for the recorded high intensity METs did not fall within the pre-determined range of >3 METs. It is unclear whether these subjects over-reported their time in high intensity activity or whether the accelerometers under-estimated energy expenditure. On average, adolescent girls were able to accurately class@ their activities into one of the three intensity categories. This method of categorizing all daily activities by intensity is useful for comparing overall activity levels at different times of the year and between subjects. It is also potentially useful in documenting results of interventions to increase physical activity for weight control.

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