Reliability and validity issues concerning large-scale surveillance of physical activity.

The BRFSS is our major source of population-based information on physical activity in the United States. The top priority for the immediate future should be to make sure that the information obtained from the BRFSS in its current form is both reliable and valid. As outlined in this report, this task could be completed in relatively short time frame and at reasonable cost in terms of both financial and human resources. The development of an additional module to assess light-to-moderate activity and strength is currently underway with support from the CDC. As suggested in this report, this task may prove to be extremely difficult, or it may be difficult to develop an instrument of this type given the constraints of a population based telephone survey. The current focus on the health benefits of moderate activity and the interest in tracking this type of activity behavior on a population basis as it relates to national physical activity objectives both argue in favor of developing a physical activity assessment instrument that provides a valid and reliable measurement of moderate activity. Given the complexity and uncertainty of this task it is important to develop a procedure that will allow for periodic evaluation of progress and the potential for success to minimize the risk of making a considerable financial investment in an instrument that may be of limited utility.