Self-report vs. objectively assessed physical activity: Which is right for public health?

Background: To examine the agreement between self-reported and objectively assessed physical activity (PA) according to current public health recommendations.

Methods: One-hundred and fourteen British University students wore a combined accelerometer and heart rate monitor (Actiheart; AHR) to estimate 24-hour energy expenditure over 7 consecutive days. Data were extracted based on population-based MET-levels recommended to improve and maintain health. On day 8, participants were randomly assigned to complete either the short-form International Physical Activity Questionnaire (IPAQ) or the Leisure-Time Exercise Questionnaire (LTEQ). Estimates of duration (IPAQ; N = 46) and frequency (LTEQ; N = 41) of PA were compared with those recorded by the AHR.

Results: Bland-Altman analysis showed the mean bias between the IPAQ and AHR to be small for moderate-intensity and total PA, however the 95% limits of agreement (LOA) were wide. The mean number of moderate bouts of PA estimated by the LTEQ was similar to those derived by the AHR but the 95% LOA between the 2 measures were large.

Conclusions: Although self-report questionnaires may provide an approximation of PA at a population level, they may not determine whether an individual is participating in the type, intensity, and amount of PA advocated in current public health recommendations.