Cool-Down You should cool down properly after each fitness conditioning period, regardless of the type of workout. The cool-down serves to gradually slow the heart rate and helps prevent pooling of the blood in the legs and feet. Your cool-down needs to begin with an activity (such as walking) to slow your heart rate. Finish off your workout by stretching. During exercise, the muscles squeeze the blood through the veins. This helps return the blood to the heart. After exercise, however, the muscles relax and no longer do this, and the blood can accumulate in the legs and feet. This can cause a person to faint. A good cool-down will help avoid this possibility.