Skeletal muscle exercise expends the stored energy of adenosine triphosphate (ATP) derived initially from the oxidation of glucose. Since most regeneration of ATP for prolonged activity is achieved directly from the oxidation of glucose brought to the muscle in the bloodstream, muscular exercise necessitates a sufficient flow of blood to the active muscles and adequate ventilation of the lungs. The experiments in this program measure the increases in heart rate, systolic pressure, respiratory rate, and tidal volume at different levels of exercise. The changes in heart and lung activity demonstrate how the exerciser copes with increasing levels of exercise. (15 minutes)