After hard exercise or physical work, the bloodstream is loaded with lactic acid, which collects in the bloodstream when there is a lack of oxygen, explains Dr. Mirkin. When the acid reaches high levels, it disrupts normal chemical reactions of the muscles and can make your muscles hurt.
"The most effective way to clear the bloodstream is to continue exercising at a slow, relaxed pace," Dr. Mirkin advises. While this may lessen immediate soreness, it won't protect you from soreness the next day. That soreness, he says, is caused by torn muscle fiber.