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. 2011 Sep;14(5):404-10.
doi: 10.1016/j.jsams.2011.03.013. Epub 2011 Apr 27.

Equating accelerometer estimates of moderate-to-vigorous physical activity: in search of the Rosetta Stone

Daniel B Bornstein  1 , Michael W Beets, Wonwoo Byun, Greg Welk, Matteo Bottai, Marsha Dowda, Russell Pate
Affiliations

Equating accelerometer estimates of moderate-to-vigorous physical activity: in search of the Rosetta Stone

Daniel B Bornstein et al. J Sci Med Sport. 2011 Sep.

Abstract

No universally accepted ActiGraph accelerometer cutpoints for quantifying moderate-to-vigorous physical activity (MVPA) exist. Estimates of MVPA from one set of cutpoints cannot be directly compared to MVPA estimates using different cutpoints, even when the same outcome units are reported (MVPA mind(-1)). The purpose of this study was to illustrate the utility of an equating system that translates reported MVPA estimates from one set of cutpoints into another, to better inform public health policy. Secondary data analysis. ActiGraph data from a large preschool project (N=419, 3-6-yr-olds, CHAMPS) was used to conduct the analyses. Conversions were made among five different published MVPA cutpoints for children: Pate (PT), Sirard (SR), Puyau (PY), Van Cauwengerghe (VC), and Freedson Equation (FR). A 10-fold cross-validation procedure was used to develop prediction equations using MVPA estimated from each of the five sets of cutpoints as the dependent variable, with estimated MVPA from one of the other four sets of cutpoints (e.g., PT MVPA predicted from FR MVPA). The mean levels of MVPA for the total sample ranged from 22.5 (PY) to 269.0 (FR) mind(-1). Across the prediction models (5 total), the median proportion of variance explained (R(2)) was 0.76 (range 0.48-0.97). The median absolute percent error was 17.2% (range 6.3-38.4%). The prediction equations developed here allow for direct comparisons between studies employing different ActiGraph cutpoints in preschool-age children. These prediction equations give public health researchers and policy makers a more concise picture of physical activity levels of preschool-aged children.

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Figures

Figure 1
Figure 1
Bland Altman plots comparing the actual MVPA estimate vs. the predicted MVPA estimate from other cutpoints. These plots represent the best and worst models from Table 1. Legend: A: Predicting Pate MVPA from Van Cauwenberghe MVPA; R2 = .97 B: Predicting Puyau MVPA from Freedson MVPA; R2 = .48
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