Background Accelerometers are popular, objective physical activity (PA) measures. However, when using accelerometry, data processing decisions must be made regarding sampling intervals (i.e., epoch lengths (EL)) and PA intensity cut-points. Objective To examine how different epoch lengths (EL) and intensity cut-points influence PA estimates among free-living, low-income Hispanic adults. Study Design, Settings, Participants This study was cross-sectional. Low-income Hispanic adults (n = 35) recruited from Expanded Food and Nutrition Education Program in five states, were asked to wear an accelerometer (ActiGraph GT3X+) for seven consecutive days. Measurable Outcome/Analysis Only data from participants with > 4 valid days (i.e., > 10 hour of wear time) were analyzed. Downloaded data were reintegrated into 1-, 10-, 30-, and 60-second ELs. Within each EL, PA cut-points were classified as either: a) sedentary; b) light; c) moderate; or d) vigorous, using two widely-accepted algorithms (Freedson and Matthews). Total moderate to vigorous PA (MVPA) was also calculated. Since the data were not normally distributed, Kruskal-Wallis analysis was used to compare the time spent in different PA intensity levels, by aforementioned ELs, for each intensity cut-point. Results The participants were mostly female (88.6%), with a mean age of 36.5 ± 11.0. Using the Freedson cut-points, the mean rank of time spent in light PA was higher for longer ELs (H = 90.7, P P P P P Conclusion This study's findings suggest that PA estimates vary by EL regardless of the cut-points used, thus validity studies should be done to compare accelerometer results with indirect calorimetry to generate the optimal EL for estimating low-income Hispanic adults’ true PA levels. Funding NIFA.
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