Author and graduation date: Deborah Alice WILLIAMS, May, 1998

Committee members: Jeanne Nichols (Chair), Donna Beshgetoor, James F. Sallis

Thesis title: Patterns of Free-Living Physical Activity in Young Adults Using the Tritrac R-3D Accelerometer

Few studies have provided objective data on weekly physical activity patterns of adults. This study examined patterns of free-living activity in young adults (n = 70, age 24.6 + 1.9 years; 43% male and 57% female) utilizing the Tritrac R-3D accelerometer. Subjects were asked to wear the device for at least 8 hours/day and preferably 12 hours/day (waking hours) for 7 days and record the times it was worn and removed. The unit was mailed to subjects, ready to be worn, in a self-adjusting hip pouch. Data were analyzed according to guidelines from the 1996 Surgeon General's Report for light (2-2.9 METs), moderate (3-5.9 METs), and vigorous (> 6 METs) physical activity using ranges of activity counts (vector magnitude) determined previously. Gender comparisons were analyzed by an independent t-test. Mean total activity minutes for the 7-day period was 544.3 (+ 237.6). The total minutes spent in light, moderate and vigorous activity were 358.1 (+ 172.7), 162.7 (+ 88.8), and 23.5 (+ 50.9), respectively.

Activity bouts were analyzed to better describe daily activity patterns. Twenty-minute bouts of moderate and vigorous activity, 10-minute moderate bouts, and 5-minute vigorous bouts were assessed. Data were separately analyzed by time of day: morning (6 a.m. - 12 p.m.), afternoon ( 12 p.m. - 5 p.m.), and evening (5 p.m.- 12 a.m.). Most activity took place during the afternoon, with 171.5 (+ 92.8) light, 77.4 (+ 53.3) moderate, and 10.0 (+ 22.0) vigorous minutes of activity. Men had significantly more total activity minutes and total moderate activity than women. Men also spent significantly more time in afternoon light and moderate activity. There were no significant differences in number of bouts of activity for men and women. These data indicate that young adults are only minimally meeting the recommendations for health-related moderate physical activity and are failing to meet the ACSM guidelines for weekly vigorous exercise.

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