P100 How Various Epoch Lengths and Activity Cut-Points Influence Physical Activity Estimates for Low-Income Hispanic Adults Under Free-Living Conditions

Abstract

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.