When lactic acid accumulation is felt, a person might slow down and lower the intensity of their activity. This will allow blood oxygen levels to return to normal. Lactic acid builds up in muscles when they are used hard or not properly recovered from previous use. Lactic acid also plays a role in immune system function. When there is too much lactate in the body, immune cells stop functioning correctly. Too much lactate can also cause nerve damage. People who work out regularly can build up lactic acid in their bodies. Because of this, they need to give their muscles time to release some of it back into the blood. If they don't, then those muscles will feel sore after working out. Sore muscles are easier to injure than healthy ones so people should try to ease off their workouts if they start to feel any pain during or after a session. In addition to releasing lactic acid from tired muscles, sweat also flushes harmful substances out of the body. Without sweating, we would be able to exercise longer without getting sick. The more intense your workout is, the more lactic acid you will build up in your muscles. To prevent muscle pain after a session, make sure to drink enough water and eat food with carbohydrates in it.