Importance of Cooling Down
After vigorous aerobic exercise it is important to take 10 minutes or so to cool down gradually. Do not stop abruptly. For example, after a long run or jog, walk around and keep moving, rather than just stopping.
Cooling down properly (moving around) redistributes the blood that may have pooled in the extremities when you end your workout, and it prevents muscle stiffness because it allows the metabolic wastes to be worked out of your muscles.