VO2 max. What is it, and why is it important?

Sorry this is so long. (and boring)

VO2 max. What is it, and why is it important?

If you’ve been around the fitness industry long enough, you’ve probably heard the term Vo2 max and probably wondered what it’s all about. My intention here is to explain it in a way that makes it understandable and to also provide some evidence as to why being cardiovascularly fit is important.
Vo2 max in scientific terms is a measurement of the maximal amount of cardiovascular exercise that someone can perform. Specifically, it’s referring to the amount of oxygen that someone can take in and deliver to working muscles to sustain aerobic exercise. It’s usually measured in mL’s of O2 per Kg of bodyweight per minute (mL/Kg/min). In general, the more oxygen you can deliver to your muscles, the more energy (ATP) you can produce. There are two main factors that determine the amount of oxygen that can be used to fuel muscles in aerobic exercise: Cardiac Output and Peripheral Adaptations.

Cardiac Output
Cardiac output is the amount of blood that your heart can pump out per minute. Two factors determine this: (1) the amount of blood pumped with each beat (stroke volume) and, (2) the amount of heart beats per minute (heart rate). SV X HR = Cardiac Output. In an endurance trained athlete, there is a dramatic increase in stroke volume, resulting in a significant increase in blood flow to peripheral muscles. The heart becomes incredibly efficient at pumping and sometimes we’ll see an increase in heart size and ventricular wall thickness (hypertrophy). This type of hypertrophy is different than that caused by heart disease.
This increase in efficiency of the heart is why most endurance trained athletes have a resting HR in the 40’s and 50’s. Basically, it takes the heart less beats to pump the same amount of blood.

Peripheral Adaptations
This refers to the extraction of oxygen from the blood by the working muscles. Two main factors determine how much oxygen can be transported into the muscles: Capillary density and Mitochondria.

Capillary Density
As an athlete becomes more cardiovasularly fit, we see an increase in capillary density within the muscles. This increase in surface area of the capillaries allows the muscles to extract a larger amount of oxygen from the blood, and deliver it to the mitochondria to produce energy.

Mitochondria
Mitochondria, which are usually referred to as the power plants of the cells are the end delivery point of the oxygen. In trained endurance athletes we see an increase in mitochondria size and numbers, allowing the processing of more oxygen and the production of more ATP.

Health Implications of Cardiovascular Exercise
It’s no secret that cardiovascular exercise is incredibly important, yet despite all of the evidence in favor of doing it, I still get the question, “should I do cardio,” and sometimes I hear a trainer or a coach make the claim that weight lifting is the only exercise that someone needs to do in order to stay healthy. Aerobic exercise is known to decrease the occurrence of risk factors like hypertension, obesity, diabetes, and hypercholesterolemia. Interestingly, VO2 max has been shown to be a strong predictor of mortality in men with heart disease, as well as healthy men. In fact, it’s been shown to be the strongest predictor of death when compared to the risk factors above. In other words, the longer you can stay on that treadmill during an exercise test, the longer you’ll live. Here comes a revolutionary idea: DO CARDIO!

If you’re interested in a simple way to test your VO2max, I have included a link that allows you to do the Rockport walking test and have it calculated for you. I’ve also attached a link to a table of percentile rankings for VO2max scores.

exphys88

http://www.exrx.net/Calculators/Rockport.html

Rockport Walk Test http://www.miracleworkout.com/form/aerobic-capacity.pdf

References:
http://www.nejm.org/doi/full/10.1056/nejmoa011858

Very nice ... thanks ExPhys88 ... nice links and glad to read that you posted the references. :D

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Originally Posted by Essie

Very nice ... thanks ExPhys88 ... nice links and glad to read that you posted the references. :D

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thank you.