We need to get oxygen from the air into the blood, and we need to remove waste carbon dioxide from the blood into the air. Moving gases like this is called gas exchange and occurs by diffusion.

Aerobic respiration occurs in the presence of oxygen, whilst anaerobic respiration occurs without it. Exchange surfaces and transport systems ... adapted for efficient gas exchange.

Most exercise scientists would agree that the physiological determinants of peak endurance performance include the capacity to transport oxygen to the working ... the demands required for ventilation ...