Why does anaerobic respiration make muscles tired and aching?
While our bodies can store glucose (for example, that’s what marathoners are doing when they eat lots of pasta the night before a race), we can’t store oxygen. Sometimes we can’t take in enough oxygen to keep up with our energy needs. When this happens, our muscle cells switch to anaerobic respiration — instead of reacting with oxygen, the glucose breaks in half and forms lactic acid. Energy is produced, but the lactic acid builds up in our muscles. This build-up makes our muscles feel heavy and they might even cramp up.
