Why does lactic acid build up in muscles? And why does it cause soreness? When our bodies perform intense exercise, we begin to breathe harder to move more oxygen to the working muscles. Sometimes our bodies make energy using aerobic methods, or with oxygen. Other times our bodies require energy production faster than our bodies can create oxygen. In these moments, the working muscles make energy anaerobically, or without oxygen. When oxygen is limited, the body converts pyruvate into lactic acid, which allows glucose breakdown. When lactic acid levels are increased, so is the acidity in our muscles. This acidity may seem to be acting against what the lactic acid is trying to accomplish, however, it is a “natural defense mechanism” for the body. It prevents permanent damage during intense exercise, by slowing the key systems needed to maintain muscle contraction. Once the body slows down and recovers, oxygen becomes easier to come by and the body goes back to making energy using aerobic methods. Some believe this lactic acid build up is the cause for the soreness you feel a day or so after intense exercise. However, lactic acid build up causes the burning sensation you feel right after or during intense exercises. This burning sensation makes the body recover so the lactic acid build up can slow down and return to normal numbers.
Research points to actual muscle cell damage, when muscles feel sore, and an elevated release of various metabolites into the tissue surrounding the muscle cells. These responses to intense exercise result in an inflammatory-repair response which may lead to swelling and soreness after the exercising. When a muscle lengthens against a load the muscle contraction is supposedly eccentric. This may result in more muscle cell damage than is seen in concentric contractions, in which a muscle successfully shortens during contraction against a load. In conclusion, exercises with the most muscle contractions, such as downhill running, result in the most DOMS, or muscle soreness. There are many anti-inflammatory medicines that solve the short term problem, but can possible harm the muscles by slowing down the time it takes