Discrepancies between Methods of Identifying Objectively Determined Physical Activity

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Abstract
Omparing published ActiGraph accelerometer intensity cut points with cut points based on intensity thresholds for heart rate response to PA. Methods: Twelve adults (five men, seven women; age 31.0 ± 14.3 yr) wore an ActiGraph accelerometer and a Polar Vantage NV heart watch simultaneously for seven consecutive days during their waking hours. We identified PA bouts from the minute-by-minute ActiGraph data using published accelerometer thresholds for defining moderate- and vigorous-intensity PA. We then compared PA bout intensities identified with these criteria with intensity classifications of the PA bouts using mean percent heart rate reserve (HRR). Results: Most of the moderate-intensity PA bouts identified by the Freedson (78.3%), Swartz (88.0%), and Hendelman (94.7%) ActiGraph cut points were associated with a mean %HRR < 45% (very light and light intensities). The estimated mean frequency with which study participants engaged in moderate-intensity PA varied with the cut points and type of bouts used and ranged from 1.1 d·wk−1 (45-60%HRR) to 7.0 d·wk−1 (Hendelman cut points). The mean total duration on active days ranged from 17.9 min·d−1 (45-60%HRR) to 139.2 min·d−1 (Hendelman cut points). Fewer bouts of vigorous PA were found in the accelerometer data, and most were in the vigorous-intensity category of ≥ 60%HRR. Conclusions: The method used for analyzing ActiGraph activity data can result in large differences in the summary measure of minutes of moderate- to vigorous-intensity activity....

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