Cool Down

Cooling down is an important aspect of your workout and should be introduced into your training; just as you ease into a running workout, you should also ease out of it by gradually decreasing your running intensity. Decreasing your intensity will allow the body's systems to return back to their pre-exercising state in a controlled manner that helps to prevent possible muscle stiffness and blood pooling.

From a safety perspective, it is important to cool down to prevent the blood from pooling in one place, notably your legs. Imagine you have just finished your workout and at this point your heart rate is 150bpm and blood is pumping furiously through your muscles. Your heart continues to pump blood at a high rate of blood flow to the muscles and with the influence of gravity this blood can quickly pool in the legs. If blood is pooled to the extent that there is not enough returned to the heart for it to maintain an effective pumping action, blood pressure may drop, lead to dizziness, nausea and fainting. In de-conditioned or unfit runners this can place undue stress on the heart and lead to cardiac complications. 

The best way to prevent blood pooling is to ease out or taper off the exercise intensity over a few minutes after the main workout; reducing pace and rate of perceived exertion.

This gradual reduction in exercise intensity over time helps both maintain cardiac output and to remove the metabolic waste products of exercise (lactic acid, carbon dioxide etc.) from the muscles.