Our bodies require energy produced through ATP synthesis. Our cells can produce ATP through the oxidation of glucose via aerobic cellular respiration or lactic acid fermentation, depending on oxygen availability. When we exercise, energy requirements increase and glucose is consumed more quickly. Also, oxygen consumption of the electron transport chain increases resulting in heavy breathing. We can measure oxygen consumption using respirometry.
In situations with low oxygen for prolonged periods of time, lactic acid can accumulate leading to lactic acidosis.
The importance of aerobic respiration is reflected in the consequences of blocking it: cells are not able to produce the energy our bodies need to maintain vital functions. This can even lead to the death of the organism. On the other hand, boosting aerobic respiration, for example by increasing oxygen availability through blood doping, leads to an increase in energy production used to improve the performance of athletes.