A Validation Study of the Web-Based Physical Activity Questionnaire Active-Q Against the GENEA Accelerometer

Abstract

Background: Valid physical activity assessment in epidemiological studies is essential to study associations with various health outcomes.

Objective: To validate the Web-based physical activity questionnaire Active-Q by comparing results of time spent at different physical activity levels with results from the GENEA accelerometer and to assess the reproducibility of Active-Q by comparing two admissions of the questionnaire.

Methods: A total of 148 men (aged 33 to 86 years) responded to Active-Q twice and wore the accelerometer during seven consecutive days on two occasions. Time spent on six different physical activity levels including sedentary, light (LPA), moderate (MPA), and vigorous (VPA) as well as additional combined categories of sedentary-to-light and moderate-to-vigorous (MVPA) physical activity was assessed. Validity of Active-Q was determined using Spearman correlation coefficients with 95% confidence intervals (CI) and the Bland-Altman method. Reproducibility was assessed using intraclass correlation coefficients (ICCs) comparing two admissions of the questionnaire.

Results: The validity correlation coefficients were statistically significant for time spent at all activity levels; sedentary (r=0.19, 95% CI: 0.04-0.34), LPA (r=0.15, 95% CI: 0.00-0.31), sedentary-to-light (r=0.35, 95% CI: 0.19-0.51), MPA (r=0.27, 95% CI: 0.12-0.42), VPA (r=0.54, 95% CI: 0.42-0.67), and MVPA (r=0.35, 95% CI: 0.21-0.48). The Bland-Altman plots showed a negative mean difference for time in LPA and positive mean differences for time spent in MPA, VPA and MVPA. The ICCs of test-retest reliability ranged between r=0.51-0.80 for the different activity levels in Active-Q.

Conclusions: More moderate and vigorous activities and less light activities were reported in Active-Q compared to accelerometer measurements. Active-Q shows comparable validity and reproducibility to other physical activity questionnaires used today.

Keywords: Internet; accelerometer; activity assessment; epidemiology; self report; validity.

Figure 1

Timeline showing participants' responses to the first and second Active-Q questionnaire and when the first and second GENEA accelerometers were worn.

Figure 2

Equation of GENEA output per minute using the post processing software. K is the number of samples per second (K=40 in our study), and x_ij, y_ij, and z_ij is the acceleration along the three dimensions, respectively, at the j:th sample of the i:th second of the particular minute. g is set to 1.00 by default.

Figure 3

Scatter plot displaying MET-values of activities performed during the calibration (x-axis) and average GENEA-output in SVMgs (y-axis) for each specific activity, n=22 (44 measuring points).

Figure 4

Bland-Altman plots illustrating differences in time spent sedentary, in light (LPA), sedentary-to-light, moderate (MPA), vigorous (VPA), and moderate-to-vigorous (MVPA) physical activity assessed with Active-Q and GENEA (y-axis) relative to the mean of the two methods (x-axis). Each point represents one study participant (n=148).