Ability of the Caltrac Accelerometer to Assess Daily Physical Activity Levels

PURPOSE: The purpose of this study was to determine the ability of the Caltrac accelerometer to assess habitual daily physical activity levels. METHODS: The ability of the Caltrac accelerometer to assess 24-hour physical activity (PA) levels was studied in 28 men and 50 women, age 20 to 59 years, with varying levels of self-reported PA. Twelve days of Caltrac readings obtained over 1 year's duration were compared to simultaneously recorded 48-hour PA records. Additionally, 28 days of Caltrac readings obtained over 1 year's duration were compared to mean values of the following validation measures assessed repeatedly over a 1-year period: a 4-week version of the Minnesota Leisure Time Physical Activity Questionnaire (FWH); VO2peak; and percent body fat. RESULTS: The Caltrac measurements of movement (in MET minutes per day-1) were significantly associated with the following: PA record indices of total (r = .51) and heavy (r = .34) and PA; FWH indices of total (r = .30), heavy R = .36) and moderate (r = .23) PA;, and VO2peak (r = .24). However, the Caltrac measurements of caloric PA record and FWH indices of PA, although there were directly associated with percent body fat (r = .50) and inversely associated with VO2peak (r = -.26). CONCLUSIONS: Caltrac measurements of movement exhibited a moderate associated with several criterion measures related to habitual PA, whereas Caltrac measurements of total energy expenditure, were not reflective of varying levels of PA.