We examined differences between objective (accelerometer) and subjective (self-report) measures of moderate-to-vigorous physical activity (MVPA) in youth. Participants included 2761 youth aged 12–19 years. Within each sex and race group, objective and self-reported measures of MVPA were poorly correlated (R2 = .01–.10). Self-reported MVPA values were higher than objective values (median: 42.4 vs. 15.0 min/d). 65.4% of participants over-reported their MVPA by 35 min/d. The difference between self-reported and objective measures was not influenced by sex, age, or race. There was, however, a systematic difference such that inactive participants over-reported their MVPA to the greatest extent.
LeBlanc is with the School of Kinesiology and Health Studies, Queen’s University, Kingston, Ontario, Canada. Janssen is with the Dept. of Community Health and Epidemiology, Queen’s University, Kingston, Ontario, Canada.