Purpose: To define and describe the essential terminology associated with dose-response issues in physical activity and health.
Methods: Recent consensus documents, position stands, and reports were used to provide reference definitions and methods of classifying physical activity and exercise.
Results: The two principal categories of physical activity are occupational physical activity (OPA) and leisure-time physical activity (LTPA). OPA is usually referenced to an 8-h d, whereas the duration of LTPA is quite variable. LTPA includes all forms of aerobic activities, structured endurance exercise programs, resistance-training programs, and sports. Energy expenditure associated with aerobic activity can be expressed in absolute terms (kJ x min(-1)), referenced to body mass (METs), or relative to some maximal physiological response (i.e., maximal heart rate (HR) or aerobic power (VO(2max))). The net cost of physical activity should be used to express energy expenditure relative to dose-response issues. The intensity of resistance training is presented in terms relative to the greatest weight that can be lifted one time in good form (1RM). The intensity of OPA followed the guidance of a previous consensus conference. The intensity of most LTPA can be categorized using the standard aerobic exercise classifications; however, for long-duration (2+ hours) LTPA, the classifications for OPA may be more appropriate.
Conclusion: Physical activities should be classified in a consistent and standardized manner in terms of both energy expenditure and the relative effort required.