To explore among demographic groups the differences in prevalence estimates of physical activity that may occur as a result of differences in survey design characteristics, including question wording, placement, and examples of activities.
We compared responses to similar physical activity instruments administered to large samples of adults in 1999 (n = 9,775), 2000 (n = 32,374), and 1999–2000 (n = 7,529). The questions assessed participation in non-occupational physical activity at vigorous and moderate intensities. Surveys used in-person or telephone interviews.
The prevalence of recommended levels of physical activity (i.e., ≥3 days and ≥20 min vigorous activities or ≥5 days and ≥30 min moderate activities) varied 10% across 3 surveys. Although survey design characteristics varied, higher prevalence was associated with the use of examples to measure multiple domains of activity and question order.
Measuring multiple domains is important for assessing health-related physical activity. These results suggest that physical activity measurement varies with question and survey design characteristics.