The Fick Equation

When you want to work on your athletic performance, measuring progress is not an easy task. You can feel the improvement by yourself, but can you truly understand it? Maybe you have noticed that you can run for longer periods of time, that you don’t get tired so easily and that there is an improvement of your overall endurance. However, these measurements are very subjective, and determined by your personal feel.

This is where the Fick Equation comes in. It allows you to calculate the improvement of your aerobic metabolism. It does so, by determining the rate at which your body uses oxygen during exercise. To put it as simple as possible:

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VO2 = Q x A – V O2 difference

Now this may seem complicated, but it really isn’t. By the time we explain everything, you’ll be the master of The Fick Equation.

While doing cardio (like ruining, cycling, swimming etc.) your body gets energy from the aerobic metabolism. Aerobic metabolism uses: oxygen, glucose, glycogen and fat, and makes ATP (adenosine triphosphate), which is used for energy. During the workout, body needs more oxygen, which is why your breathing becomes faster and deeper, and your heart rate increases. By measuring your VO2, you can find out what is the upper limit of your aerobic metabolism.

VO2 is the volume of oxygen uptake. Maximum VO2 is the highest amount of oxygen your body can take and use. It is determined by genetics and training. Greater VO2 means that your body is more efficient at delivering oxygen to cells and using it. There are two important components to this:

  1. Oxygen delivered to cells and
  2. The amount of oxygen used by the cells.

Oxygen delivered to cells refers to the amount of oxygen that cells get. This varies from person to person, and is calculated by determining cardiac output. Cardiac output (Q) is the amount of blood pumped by the heart per minute. It is made of two parts: blood pumped by the heart beat (stroke volume – SV) and beats per minute (hear rate – HR). So Q = SV x HR .

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The amount of oxygen used by the cells is called oxygen extraction. It can tell us how much oxygen is actually taken from the blood and used by the cells.. The difference in oxygen saturation in arteries (A) and veins (V) is used to calculate oxygen extraction. Simply put arterio – venous difference = A – V O2.

When you put this all together you get The Fick Equation. Oxygen uptake = cardiac output x arterio – venous difference, or in math terms VO2 = Q x A – V O2.

To increase VO2 both components must be affected:

  1. Increase cardiac output (Q), so oxygen travels through the body faster, and is easily available and
  2. Increase A – V O2 difference. This way the amount of oxygen used by the cells is greatly improved.

All of this translates to greater and more efficient aerobic metabolism, which means improvement in athletes’ performance.


The Fick Equation
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