Aspects of oxygen consumption: Oxygen deficit, steady state and EPOC

When the body begins exercise there is an increase in oxygen demand by the muscles in order to produce increased amounts of ATP. To do this the body employs the use of acute cardiovascular and respiratory changes in order to provide the muscles with the required oxygen. However these systems take a while to come into effect therefore anaerobic pathways will be increasingly relied upon. Thus leading to oxygen deficit at the commencement of exercise, a steady state that is achieved during exercise and exercise post oxygen consumption(EPOC) which occurs after exercise.


(image from Live it up 2: VCE physical education Units 3 & 4 )

Mechanisms of oxygen consumption

Oxygen deficit

Is the point where exercise is commenced and there is an increase in oxygen demand, to meet the increased oxygen requirements the body initiates its actuate cardiovascular and respiratory changes. However these changes take a while to come into effect, therefore the body is not supplying the oxygen required by the muscles. This deficit in oxygen supply leads to the body relying on anaerobic pathways that produce harmful metabolic by-products, these harmful metabolic by-products require oxygen to be broken down properly. The metabolic by-products sit in the body until there is enough oxygen to break them down properly creating an oxygen debt needing to be repaid.

Steady state (oxygen consumption)

The period of exercise where the body’s acute cardiovascular and respiratory changes have come into effect and the body is able to produce enough oxygen to meet demand.

Exercise post oxygen consumption (EPOC)

Is the excess amount of oxygen consumed by the body after exercise is finished that is above normal levels of oxygen required for rest. This excess oxygen is used to breakdown metabolic by-products produced by the anaerobic pathways, therefore the body in a sense repays the oxygen debt owed.
It should be noted that students in the exam may need to be able to identify features of the graph above in exams, it should also be noted that the x-axis begins from normal resting levels not at zero oxygen consumption.