Measurement of physical activity, exercise, and physical fitness in children: issues and concerns.

Data to support the type and level of physical activity that are necessary for health benefits in children and for later prevention of disease as adults are not available. This lack of information may be caused by inconsistency in terminology and by issues and concerns with available instruments to measure the concept. The purpose of this article is to address measurement issues related to physical activity/exercise or physical fitness in children. Implications of these issues for researchers and practitioners are discussed.