WHY  DOES  LACTIC  ACID  BUILD  UP  IN  MUSCLE?

During aerobic exercise our muscle ‘burn’ glucose with oxygen to produce carbon dioxide, water and energy. But when we are exercising hard, the lungs can’t keep up with the muscles’ demand for oxygen. Rather than just giving up, our muscle switch to an anaerobic chemical chemical reaction that doesn’t need oxygen.

This is less efficient because it doesn’t produce as much as enegy per molecule of glucose burned, but it’s better than nothing. Unfortunately, instead of water and carbon dioxide, anaerobic respiration produces lactic acid as one of it’s waste products. If you exercise hard, this will be produced faster than your bloodstream can transport it away to your liver where it is processed and broken down.

As the level of acid builds up in your muscles, you feel a burning sensation that acts as a warning that your muscle are almost out of energy. Like other sorts of pain, the ‘purpose’ is to signal that your body needs to rest. So, next time you go for a run bear your overworked body a thought and maybe catch your breath.