[Robert Riddell is a Senior at the East Carolina University and is currently enrolled in the Athletic Lab Coach Apprenticseship Program] While many think fatigue and soreness is caused by the accumulation of lactic acid this is an old myth that hasn't died. Lactic Acid For energy, our muscles use glucose and glycogen during exercise. When these energy sources are broken down, our body produces what is called lactic acid. This acid is the "burning" sensation felt when working our muscles, which can also be attributed to low oxygen levels in the muscle, as well as the recruitment of fast twitch fibers. Removing lactic acid from the blood may be aided by performing a "cool down" immediately following exercise. Research indicates that lactic acid levels in the blood return to normal within 40 minutes of a cool down, as opposed to 60 minutes without. Lactic acid, however, is not the reason you are sore after intense exercise. Muscle soreness is something that effects us a day or two after a heavy bout of activity. This is referred to as DOMs or, delayed onset muscle soreness. DOM's in actuality is a type 1 muscle strain associated with pain that restricts movement. Pain varies from light to severe stiffness (Braun). What is soreness Soreness is the result of the breaking down of muscle proteins. Muscle fibers are torn during contractions that produce high force. An inflammatory-repair response is initiated, which is responsible for the pain, tenderness, and immobility of the muscle (Kenney). The body is not used to performing muscle-lengthening exercises. Because of this, eccentric movements cause more damage than concentric movements (Kedlaya). Due to fewer motor units being activated during eccentric than concentric contractions, force is [...]