After a vigorous exercise or work we feel pain in muscles

After a vigorous exercise or work we feel pain in muscles. What is the relationship between pain and respiration ?
**A.**1) We obtain energy by aerobic respiration. .
2) But anaerobic respiration can sometimes take place in our muscles.
3) During vigorous exercise oxygen gets used up faster in the muscle cells that can be supplied by the blood.
4) When anaerobic respiration takes place in human muscles, glucose is converted into lactic acid with the release of a small amount of energy.
5) The anaerobic respiration by muscles bring about partial breakdown of glucose to form lactic acid.
6) The accumulation of lactic acid in the muscles causes muscular pains or cramps.