Discusses how to teach aerobic fitness concepts to elementary students. Some of the K-2 activities include location, size, and purpose of the heart and lungs; the exercise pulse; respiration rate; and activities to measure aerobic endurance. Some of the 3-6 activities include: definition of aerobic endurance; heart disease risk factors; circulatory/respiratory system; intensity guidelines; specificity principle; overload/progression principles; and activities to measure aerobic endurance. (SM)