[Accelerometry does not match with self-reported physical activity and sedentary behaviors in Mexican children]

An accurate assessment of physical activity in schoolchildren is necessary to implement strategies that promote active lifestyles. The objective of this study was to validate a self-administered questionnaire to assess physical activity and sedentary behaviors and to analyze differences in the validity according to nutritional status in Mexican schoolchildren.

Schoolchildren of 8-12 years of age answered a self-report physical activity and sedentary behaviors questionnaire to evaluate sedentary and light physical activity (SLPA) and moderate to vigorous physical activity (MVPA). The data of children who wore a triaxial accelerometer days was analyzed. Concordance between both methods to determine the time schoolchildren spend watching television was assessed using intraclass correlation coefficients and Bland-Altman method.

The estimation of MVPA by questionnaires was higher than that of accelerometers by 117.6minutes per week, and the estimation of SLPA was lower by 1,924.7minutes per week. No correlation between the time assessed by accelerometers and the time reported in the questionnaires for SLPA and MVPA was detected. In normal-weighted children, a low correlation between the time dedicated to play videogames with sedentary activities (r_ic=0.29, p=0.031) assessed by accelerometers was observed.

Schoolchildren over-estimate MVPA and under-estimate SLPA. Body weight can be a factor influencing such bias.