Moderate-to-vigorous physical activity among children: discrepancies in accelerometry-based cut-off points.
OBJECTIVE
To highlight the discrepancies in accelerometry cut-off points of moderate-to-vigorous physical activity (MVPA) according to the definitions of Puyau et al. (MVPA(P)) and Trost et al. (MVPA(T)).


METHODS
Forty-five children from 8 to 11 years old were monitored with the ActiGraph (ActiGraph, LLC, Fort Walton Beach, FL) for 3 consecutive days. Daily time spent at MVPA obtained with MVPA(P) was compared with that obtained with MVPA(T) using variability, regression, and agreement statistics. Data were then discussed with regard to physical activity recommendations.


RESULTS
The mean daily time spent at MVPA(P) (28 +/- 18 minutes) was significantly lower (p < 10(-4)) than that spent at MVPA(T) (141 +/- 39 minutes). The coefficient of determination between the two definitions was low (R(2) = 0.49 +/- 0.71). There was a lack of agreement between the two definitions, with a mean error or bias of 113 min/d. Thirty-four point eight percent and 100% of children underwent 30-minute MVPA/d with MVPA(P) and MVPA(T) definitions, respectively.


CONCLUSIONS
Comparability between studies devoted to describing children's physical activity or to assessing interventions may lack consistency according to the definition, with a real risk of misclassification.
Guinhouya
Comlavi B
CB
EA 3614, Modelling Complex Systems, Medical Decision Support, Institute of Engineering in Health of Lille, University of Lille 2, 42 rue Ambroise Paré, F- 59120 Loos, France.
Hubert
Hervé
H
Soubrier
Stéphane
S
Vilhelm
Christian
C
Lemdani
Mohamed
M
Durocher
Alain
A
D002648:Child; D016552:Ergometry / Q000379:methods / Q000592:standards* / Q000706:statistics & numerical data; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D013997:Time Factors