ABSOLUTE VERSUS RELATIVE INTENSITY CLASSIFICATION OF PHYSICAL ACTIVITY: IMPLICATIONS FOR PUBLIC HEALTH POLICY.

A major issue in evaluating the success of educational programs intended to improve public participation in physical activity is how to classify the intensity of activities performed. Currently, there are at least two approaches to estimating intensity of leisure time physical activity (LTPA), based on relative and absolute scales. We examined the impact of using relative versus absolute criteria on reaching physical activity goals set by the American College of Sports Medicine (ACSM; 2000) and the Surgeon General (United States Department of Health and Human Services, USDHHS, 1996). Subjects were healthy men (n = 619) and women (n = 497) aged 18-95 who were participants in the Baltimore Longitudinal Study of Aging. The percentage of subjects meeting the Surgeon General's recommendations for moderate and high intensity LTPA declined with age under the absolute classification system but increased with age when a relative intensity scale was used. Using ACSM recommendations, aging was associated with a decline in high absolute intensity LTPA. However, when a relative classification system was used, high relative intensity LTPA appeared to increase with age, inverting the relationship between high-intensity LTPA and cardiorespiratory fitness. The use of relative intensity LTPA criteria suggests that older subjects are meeting national standards for physical activity, raising questions about the appropriateness of such a scale to motivate older adults to improve their fitness. [ABSTRACT FROM AUTHOR]