Essa dissertação é composta por dois manuscritos: Artigo de Revisão: Validity and reliability of questionnaires that assess barriers and facilitators of sedentary behavior in the pediatric population. A systematic review. - O objetivo de nossa revisão foi avaliar a validade e a confiabilidade de questionários que abordam as barreiras e facilitadores percebidos do comportamento sedentário em crianças e adolescentes de 2 a 19 anos. Além disso, nossa revisão pretendeu identificar os principais fatores associados ao comportamento sedentário. Artigo Original: Confiabilidade e validação de um questionário sobre barreiras e facilitadores percebidos do comportamento sedentário em crianças e adolescentes da América do Sul - (i)Testar a confiabilidade (teste-reteste) de um novo e inovador questionário de barreiras e facilitadores do comportamento sedentário em crianças e adolescentes da América do Sul; (ii) e a validade critério do questionário com o tempo sedentário mensurado por acelerômetro.

Technological advances and prolonged exposure to screens are directly associated with sedentary behavior in the pediatric population. As a consequence, there is an increase in cardiovascular risk factors and obesity, which can accompany the individual in adult life. In this sense, studying the psychometric properties of instruments allows us to understand the level of reliability and validity of the barriers and facilitators of sedentary behavior in the questionnaires, which is important in terms of guiding health prevention strategies and their aggravating factors. Objective: (i) test the reliability (test-retest) of a questionnaire on barriers and facilitators of sedentary behavior in children and adolescents in South America; (ii) test the predictive validity of the questionnaire with sedentary time measured by accelerometry. Methodology: The SAYCARE Study is an observational multicenter feasibility study in a sample of children and adolescents aged 3 to 18 years (children: n= 237 adolescents n= 273. This pilot was developed in São Paulo and six other cities in North America South: Teresina (Brazil), Buenos Aires (Argentina), Santiago (Chile), Montevideo (Uruguay), Lima (Peru) and Medellín (Colombia). The questionnaire was applied twice with an interval of two weeks and the behaviors were reported by the parents for children and self-reported for adolescents. The accelerometer was used for at least 3 days, including at least one weekend day. We will compare sedentary time values using accelerometers by time quartiles of sedentary time measured. For analysis statistics, descriptive analyzes were used (mean, median, standard deviation and proportions) questionary and the agreement was mild and for the adolescents the reliability was moderate with higher agreement as well. For the factor analysis, two factors were obtained (children: Factor 1- 0.25992 to 0.34477 and Factor 2 -0.27831 to 0.35565) and (adolescents Factor 1 from 0.26403 and Factor 2 from 0.29266 to 0.32431). Spearman's correlation showed low to moderate values in comparison between Q1 and the use of accelerometry data.