Abstract
Objective: This investigation aimed to psychometrically validate an accelerometer index against a self-reported questionnaire in a sample of female adolescents. Methods: This analysis was based on a multicentric prospective randomized controlled trial among adolescent girls aged 12 to 14 years. Accelerometer devices were given to participants to be worn on their person for seven consecutive days, after completing a self-administered questionnaire. The "Brazilian Economic Classification" was used to rank participants according to socioeconomic strata. Results: There were 195 participants with an average age of 13.4 ± 0.65 years, 10.8% obese and 51% physically inactive. Participants in the medium-high class were less physically active. The participants in medium-low class presented higher METs [1.03 (±0.03)]. Exploratory factor analysis demonstrated a two-factor structure, labeled Daily Physical Activity and Sedentary Activity, with good factor loadings and internal reliability scores, as well as appropriate validity across a range of self-reported physical activity measures. Conclusion: Results allow us to reflect about the use of instruments to evaluate interventions directed to weight related problems.