Validity and reproducibility of a physical activity and inactivity questionnaire for Mexico City's schoolchildren.

Objective. To assess the validity and reproducibility of a self-reported qu estionnaire on physical activity and inactivity, developed for children age d 10-14 in Mexico City. Material and methods. Between May and December 1996 , a self-reported physical activity and inactivity questionnaire was develo ped and applied twice to a sample of 114 students aged 10 to 14, from a low and middle income population of Mexico City. The children's mothers comple ted the same questionnaire, and two 24-hour recalls of physical activity we re used for comparison. Statistical analysis consisted of central tendency and dispersion measures and Pearson's correlation coefficient. Results. Cor relations between hours per day spent in physical activity and inactivity f rom the children's questionnaire and the 24-hour recall data, were 0.03 for moderate activity, 0.15 for vigorous activity, and 0.51 (p=0.001) for watc hing television, adjusted by age, gender, town, and illness prior to the ad ministration of the questionnaire. Compared to the 24-hour recall data, the questionnaire overestimated the time spent watching television, reading or participating in vigorous activity, and underestimated the time engaged in moderate activity. Statistically significant (p<0.05) six-month reproducib ility values were observed for watching television (r=0.53), sleeping (r= 0 .40), moderate (r=0.38), and vigorous activity (r=0.55). Conclusions. Among children of Mexico City aged 10-14, the questionnaire showed acceptable va lidity in estimating the time watching television, and acceptable reproduci bility of the time watching television, vigorous and moderate activity.