Ahh the good old Fick Equation
VO2 = Q x A-VO2 diff.
During every activity we are using some percentage of our maximum VO2. But how do we measure VO2? Well, we look at two things: 1) the amount of oxygen delivered to the cells and 2) how much oxygen is used by the cells.
1.The oxygen delivery to cells is calculated by determining cardiac output (amount of blood pumped per minute). Cardiac output (aka Q) is made up of two components – how much blood is pumped per beat (aka stroke volume) and how many times the heart beats per minute (aka heart rate). The short version? Cardiac output is equal to stroke volume times heart rate. The really short version? Q = SV x HR
2.How much oxygen is used by the cells is called oxygen extraction. Oxygen extraction looks at how much oxygen is taken from the blood to be used by the cells to make ATP for energy. Oxygen extraction rates are measured by the difference in oxygen saturation of the blood going to the tissues (in the arteries) and of the blood returning to the heart (in the veins). This is known as the arterio-venous difference or A-VO2 difference.
Do you see how the Fick equation comes together now? You take your Q and your A-VO2 and put them together. Vo2 = Q x A-VO2 difference Do you see the importance of understanding Fick? If you know what components make up aerobic capacity (HR, SV, A-VO2 diff) you may have a better understanding of how you can influence those variables to increase an individual’s Max VO2.