fundamentals
Exercising Safely
Cooling down
Slowing down gradually (cooling down) at the end of exercise helps prevent light-headedness. When the leg muscles relax, blood collects (pools) in the veins near them. To return the blood toward the heart, the leg muscles must contract. When exercise is suddenly stopped, blood pools in the legs and not enough blood goes to the brain, causing light-headedness. By preventing blood from pooling, cooling down also helps the bloodstream speed up its removal of lactic acid, a natural chemical product that builds up in the muscles during exercise and that can unduly strain the body if it accumulates. Some ways to cool down include walking for a few minutes (after a run), doing 1 to 2 light weight training sets (after more intense sets), and stretching. 