You should not stop suddenly after running very fast or doing any other very intense exercise, because it may cause you to pass out.
During running, your leg muscles serve as a second heart. When your leg muscles relax, the veins near them fill up with blood. When your leg muscles contract, they push against the veins near them and squeeze the blood toward your heart. If you exercise vigorously and stop suddenly, the leg muscles stop contracting and blood can pool in your legs, so not enough blood passes to your brain and you can pass out. When you slow down gradually, you allow time for your heart to pump harder to make up for the loss of pumping by your legs. Cooling down does not prevent muscle soreness, which is caused by a tearing of muscle fibers during exercise, not by the buildup of lactic acid when you run so fast that you can't get enough oxygen.
People Also Search For: