Calibration Of Triaxial Accelerometer Actigraph GT3X In Boys Aged9to11Years

PurposeDevelop an equation from the ActiGraph GT3X output for predict the energyexpenditure of physical activities and cut off point for classify the light physicalactivities(LPA) and moderate-vigorous activities(MVPA), validate the accuracy ofenergy expenditure predicted by Trost equation, Freedson age-specific equation、Puyau equation、Treuth equation、Schmitz equation、Mattocks equation and theaccuracy of classification of LPA and MVPA by the corresponding cut off point andEvenson cut off point. Provide methodological support for study in boys aged9to11years when using ActiGraph GT3X in the future.Methods63boys were recruited from Shanghai liuyi elementary school in this study.Participants wore one ActiGraph Accelerometer GT3X on their right waist duringeach test and their oxygen consumption was measured using Cosmed K4b2.，completed tests of resting metabolic rate, six5minutes treadmill activity conditions(3,4,5,6,7km.h-1), one of the third sets of the elementary and middle school studentbroadcast gymnastics (Xiwangfengfan4min and38sec) and two table tennisexercises (continuous attack for5min, mult balls for3min). Set the measured valueof Cosmed K4b2as the criterion, develop an equation from the ActiGraph GT3Xoutput for predict the energy expenditure of physical activities and cut off point forMVPAData analysesData analyses were performed in SPSS17.0. Data were summarized as means±SD. The63participants were randomly divided into developmental group (n=51,80%) andvalidity group (n=12,20%). In the developmental group, the person correlationcoefficients were used to assess the relationship of the variables, The triaxial vectormagnitude counts (VM), weight, height, sex, age and body mass index(BMI) wereused to develop the equation for predict energy expenditure by stepwise multiplelinear regression. Use the receiver operating characteristic curve (ROC) to determine the cutoff point for MVPA, the minimum error rate as the criterion. In the validity group, the differencebetween measured and predicted energy expenditure was evaluated using pairwise t-tests. Thepredictive accuracy of equation was compared by calculating the percent of difference between themeasured and predicted values. Classification accuracy of LPA and MVPA was evaluated througharea under the receiver operating characteristic curve (ROC-AUC). For all analyses, statisticalsignificance was set at p<0.05.Results1.For eight activities combined，correlations between energy expenditure and thetriaxial vector magnitude counts (VM) was the highest(r=0.71，P<0.01), using VM,weight as independent variables, energy expenditure as the dependent variable,develop energy expenditure prediction equation：EE（kcal/min） =0.00059×VM+0.052×weight-0.616(R2=0.628,SEE=0.98kcal/min)。2. In the validity group, we validated the accuracy of the energy expenditure predictedby equation. For eight activities combined, Trost equation significantly overestimatedthe EE (24.7%), Freedson age-specific equation significantly overestimated the METs(50.6%), Puyau equation significantly underestimated the AEE (32.7%), Treuthequation significantly overestimated the METs (34.2%), Mattocks equationsignificantly underestimated the EE (45.4%). The new equation and Schmitz equationcan predict the energy expenditure better.3. Using the ROC to develop cut off point for MVPA (VM≥4100), the ROC-AUC was0.848.4. In the validity group, we validated the accuracy of classification of LPA and MVPAby equation and cut off point. The ROC-AUC of new cut off points was0.794,followed by0.753for Treuth equation、Treuth、Evenson cut off point.0.739for Puyaucut off point,0.727for Mattocks cut off points and0.679for Freedson age-specificequation. Freedson age-specific equation、Treuth equation and Evenson cut off pointsmisclassified57.3%、42.7%、42.7%of LPA to MVPA respectively, Puyau、Mattockscut off points misclassified29.5%、38.6%of MVPA to LPA respectively.Conclusion1. For eight activities combined, Trost equation、Freedson age-specific equation、Puyau equation、Treuth equation、Mattocks equation significantly overestimated orunderestimated the energy expenditure. The new equation and Schmitz equation canpredict the energy expenditure of common physical activities better in boys aged9to11years.2. Freedson age-specific equation、Treuth equation and Evenson cut off points tendedto misclassify the LPA to MVPA, leading to potential overestimation of time spent inMVPA; Puyau and Mattocks cut off points tended to misclassify MVPA to LPA,leading to potential underestimation of time spent in MVPA. Compared with theequations and cut off points, the accuracy of the new and Treuth cut off points forclassify the LPA and MVPA in boys aged9to11years were higher than the others.