OBJECTIVETo evaluate the use of a 7-day physical activity questionnaire in epidemiologic studies on 4-6th grades children.

METHODSFocus group discussion, observation and expert consultation were used to develop 7-day physical activity questionnaire. The reliability and validity of questionnaire were determined in a sample of 92 children in 4-6th grades who were randomly selected from four schools in urban Beijing. A two-week test-retest reliability was determined. The questionnaire was validated against experts' evaluation and Caltrac motion sensor.

RESULTSFor different measures of activity, the agreement was good between the test and retest. Kappa values ranged from 0.46 to 0.79, and the Spearman correlations ranged from 0.66 to 0.87 in boys and 0.57 to 0.82 in girls, with significant difference (P < 0.01). The face validity and content validity were good by experts' evaluation. There was no significant difference between questionnaire results and Caltrac motion sensor for both boys and girls, and the questionnaire correlated significantly (r = 0.46, 0.38 for different measures of activity) with Caltrac motion sensor for boys.

CONCLUSIONThese data provided evidence that the 7-day physical activity questionnaire yield a reliable estimate of past week physical activity for 4 - 6-grade children and provided valid estimation of past week physical activity for boys.