Validity, reliability, and readability of single-item and short physical activity questionnaires for use in surveillance: A systematic review.

Background: Accurate and fast measurement of physical activity is important for surveillance. Even though many physical activity questionnaires (PAQ) are currently used in research, it is unclear which of them is the most reliable, valid, and easy to use. This systematic review aimed to identify existing brief PAQs, describe and compare their measurement properties, and assess their level of readability.