Comparison between self-reported and pedometer-measured physical activity in Vietnamese adolescents: A reliability and agreement study.

To compare the level of physical activity (PA) measured by self-reported questionnaire and pedometer in 12-year-old Vietnamese adolescents. Data was collected from March to May 2023 in two phases among 510 sixth-grade students in Ho Chi Minh City, Vietnam. The first phase involved a pilot study, which recruited 35 students from a randomly selected class to evaluate the Physical Activity Questionnaire for Older Children (PAQ-C) test-retest reliability. PA was measured twice, with seven-day intervals between assessments. The second phase was a cross-sectional study including 475 sixth-grade students to evaluate the agreement between PAQ-C scores and pedometer data. Participants wore a pedometer continuously for seven days and completed the PAQ-C at the end of the monitoring period. Sociodemographic and anthropometric data were collected. The sample of 35 students showed that PAQ-C demonstrated good internal consistency (α = 0.89) and test-retest reliability (ICC = 0.82). After one week, McNemar's test indicated no significant difference in activity levels between the baseline and second assessment. In the sample of 475 students, there was a substantial agreement between PAQ-C and pedometer in classifying physical activity levels (Cohen's κ = 0.688, p < 0.001), with a strong correlation between daily step counts and PAQ-C scores (rs = 0.855, p < 0.001). PAQ-C is a reliable, cost-effective tool for school-based PA monitoring in 12-year-old Vietnamese adolescents, particularly in resource-limited settings.