What is VO2 Max?

By Scott Black, M.D., M.S.

 Most endurance athletes are familiar with the term “VO2max”.  It is not uncommon to overhear runners or cyclists discussing in admiration the fact that Lance Armstrong (or another world-class endurance athlete) has a “V02max of close to 80”.  For the most part, we all know that athletes with higher numbers generally perform better, but just what is a V02max and is it an important measurement that any competitive endurance athlete should have measured?

V02max is shorthand for the volume of oxygen that the body can consume at maximal effort.  It is a measure of an individual’s aerobic capacity.  As muscles work, they consume oxygen.  Think of your muscles like a car engine.  Cars burn a mixture of fuel and oxygen to produce work.  Your muscles do the same thing.  Carbohydrates or fat (fuel) are consumed along with oxygen and work is produced.  Larger, more powerful engines generally consume more fuel and oxygen and can produce more work.  Compare a Corvette and a Prius.  The Corvette is faster but consumes more fuel and oxygen.

As a general rule of thumb, individuals who can consume more oxygen also can do more muscular work and therefore are better at endurance sports.  Likewise, improving one’s VO2max has the potential of improving race performance as well.

There are two ways that you can have your aerobic capacity assessed.  If you are a runner, you can simply estimate your VO2max based on race results for your most recent two or three races.  Charts that give you an estimated value are available in a number of resources.  One of the classic books that contain this information is Daniels’ Running Formula by Jack Daniels, PhD.  I haven’t seen similar charts for cyclists, but Chris Carmichael (Lance’s coach) advocates using a three-mile maximum effort time trial on a regular basis to evaluate your current abilities.  Alternatively, a submaximal test called the Astrand Test has been developed to estimate a cyclist’s maximal oxygen uptake.  Information on how to perform this test can be found by checking with a fitness professional.

On the other hand, if you are into technology and want a direct measurement of your VO2max, this can be accomplished in a laboratory during a maximum cardiopulmonary exercise test.  First, you have to find a lab with the proper equipment to perform the test.  University exercise physiology labs usually have a metabolic cart, which is the device that measures your oxygen consumption and carbon dioxide production during exercise.  Some medical centers, especially ones that provide cardiac or pulmonary rehabilitation services, are also likely to have metabolic carts.  Alternatively, some private labs or training facilities are beginning to offer this service.

During the test, you will exercise on either a treadmill or a stationary bicycle.  Runners should use a treadmill and cyclists should exercise on a bike.  While you are exercising, you will have to breathe through a mouthpiece connected by a tube to the metabolic cart.  The cart will analyze how much oxygen you’re consuming and carbon dioxide you’re producing.  You will be asked to gradually increase the intensity of your exercise until you can’t work any harder and ask to stop.  The amount of oxygen you’re consuming at that time is your VO2max.  The other key pieces of information you will need from the test are your maximum heart rate at the end of the test and the treadmill velocity at your V02max.  For cyclists, your maximum power output can be substituted for treadmill speed.

Once you have determined your VO2max (either by estimation or direct measurement), your maximum heart rate, and either your running speed or cycling power output that corresponds to your maximum oxygen consumption, you can use that information as an objective measure of your current aerobic capacity.  Interval or threshold workouts can be planned at more exact intensities.  Later, a higher VO2max or improved time trial performance on a repeat test can demonstrate the effectiveness of your training program.  No change might indicate that you need to alter your routine.

Be aware, however, that VO2max is not the only factor that influences your race day performance.  While it is true that a high aerobic capacity is a pre-requisite for being an elite endurance athlete (have you ever seen a Prius in a Nascar race?), many other factors play a role in your final race time.  Lactate threshold, exercise economy, motivation, and plain old toughness all significantly influence your race performance such that the person with the highest VO2max doesn’t always win.

Dr. Black is an avid runner, cyclist, and multi-sport athlete.  He has a Master’s degree in exercise physiology from the University of Kentucky.  He also received his medical degree and completed a Family Medicine residency at UK.  After ten years in private practice he completed a Sports Medicine fellowship at Wake Forest.

Image from: www.boulderperformancelab.com/



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