Accelerometers thresholds to estimate physical activity intensity in children and adolescents: a systematic review

The aim of this study was to verify the criterion and cross-validity of accelerometer thresholds for distinguishing different physical activity intensities and identifying sedentary behavior in children and adolescents. A systematic literature review was conducted using the PubMed, Scopus, Sports Discus and Web of Science databases. Inclusion criteria were: a) derivation and/or validation of accelerometer thresholds related to intensity of physical activity in youth (age 2 to 18 years); b) use of indirect calorimetry or direct observation as the reference method; c) original research articles published in English, Portuguese or Spanish. Nineteen studies were selected. The accelerometers most often investigated were ActiGraph, RT3 and Actical. Thresholds showed good to moderate validity in the calibration phase (sensitivity = 68 to 100%; specificity = 61 to 100%). Generalizability of the thresholds was higher when they were tested on independent samples (Kappa = 0.72 to 0.91; sensitivity = 79 to 94%; specificity = 72 to 98%) than during independent activities (Kappa = 0.46 to 0.71; sensitivity = 27 to 97%; specificity = 52 to 95%). One calibration study tested the validity of thresholds in independent samples and activities, and only one threshold validation study was found. In conclusion, limited information is available on the generality of accelerometer thresholds for physical activity monitoring in children and adolescents. Validation studies are needed to identify appropriate thresholds for each type of accelerometer.Original Abstract: O objetivo deste estudo foi verificar a validade (criterio) e a generalidade (validade cruzada) dos limiares de acelerometros para distinguir diferentes intensidades de atividade fisica em criancas e adolescentes. Uma busca sistemdtica da literatura foi conduzida nas bases de dados Pubmed, Scopus, Sports Discus e Web of Science. Os critirios de inclusao foram: a) derivacao e/ou validacao de limiares de acelerdmetros relacionados a intensidade da atividade fisica em jovens (2 a 18 anos); b) uso da calorimetria indireta ou a observacao direta como metodo de referencia e; c) estudos em lingua inglesa, espanhola ou portuguesa. Dezenove estudos foram selecionados. Os acelerdmetros mais investigados foram o ActiGraph, o RT3 e o Actical. Os limiares apresentaram boa a moderada validade na fase de calibraco (sensibilidade = 68-100%; especificidade = 61-100%). A generalidade dos limiares foi maior quando estes foram testados em a