Response to exercise

Muscles need energy to contract. During exercise:

  • the breathing rate and volume of each breath increases to bring more oxygen into the body and remove the carbon dioxide produced
  • the heart rate increases, so that blood supplies the muscles with oxygen more quickly and removes the carbon dioxide produced more quickly

If insufficient oxygen is available to the muscles the heart and lungs are unable to supply sufficient oxygen. This happens when exercise is vigorous and/or prolonged.

As a result, muscle cells cannot support the electron transport chain. They begin to respire anaerobically. Instead of carbon dioxide, water and ATP being produced, pyruvate is converted to lactate. Muscles continue to contract, but less efficiently.