What is the relationship between vo2 max and cardiac output?

Answer 1

Cardiac output is the amount of blood that cardiac muscle is pumping out within one minute. it is measured in liters per minute.

VO2 maxmeans maximal oxygen consumption, maximal oxygen consumption is the maximum capacity of an individual's body to transport and use oxygen during maximum work. It is measured in milliliters per minute per 1kg of working muscle.

Some factor's are affected in this relationship .

Oxygen carrying capacity of the blood -- how much oxygen is your blood carrying per unit of blood -- typically expressed in ml of oxygen per 100 ml of blood or per liter of blood.

The amount of oxygen blood is carrying is a function of how much hemoglobin you have in your blood and the pressure of oxygen (PO2) in the arteries that are delivering the blood.

Each gram of hemoglobin can carry 1.34ml of oxygen, if fully saturated (as it pretty closely is at sea level), so if we have hemoglobin count of 15 this means we can carry about 20 (15X1.34)ml oxygen per 100 ml blood or 200 ml per 1 liter of blood. Since we are only about 97% saturated the numbers become about 19 or 190.

Then if we can pump 20 liters per minute (20-liter cardiac output), we can deliver 3800ml oxygen per minute -- 190 per liter X 20 liters. Obviously if we reach a cardiac output of 30 liter per minute then we could deliver 5700ml O2 per minute. Also, if we have less hemoglobin or at altitude where the hemoglobin is not as saturated with oxygen, then we will deliver the same amount of blood but less oxygen.

Anyway VO2 max depends on how much oxygen we can deliver (the central factor) and at the exercising muscle, how much of the delivered oxygen can the muscle use per minute to convert fuel into energy

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Vo2 max can be defined by Fick equation

Q is the cardiac output of the heart, CaO2 is the arterial oxygen content, and CvO2 is the venous oxygen content, from the Fick equation it can be seen that Vo2 max has a linear relationship with cardiac output

Vo2 = cardiac output x AVo2 difference....

Cardiac output = HR x stroke volume

Stroke volume: Determined by size and strength of heart muscle tissue.

AVo2 difference = Measures how much oxygen is taken up by the muscles. The difference in arterial vs venues blood oxygen content.

Blood comes to the muscles via arteries. Number of capillaries and mitochondria is the main determining factor how much oxygen is taken up by the muscles. Capillaries take the blood deep into the muscle and across more muscle. Oxygen is then "dropped off" at the mitochondria IF it is needed. More mitochondria, more need.

The more changeable factor here is the A Vo2 difference