VO2 max - Maximal Oxygen Uptake

By Rick Morris

One of the most basic physiological indicators of your fitness and running performance is your VO2 max. VO2 max or maximal oxygen uptake is a measure of how much oxygen your body can process to produce energy. It is measured in milliliters of oxygen per kilogram of body weight per minute – ml/kg/min. When you increase your running speed your body demands more and more energy to keep you on pace. To produce all of that energy your body uses up a lot of oxygen. Eventually you reach the level at which your body maxes out its ability to deliver and extract oxygen. At that point your oxygen consumption has reached its peak and remains mostly steady. At that level of exercise you have reached your VO2 max or maximal oxygen uptake. Any increases in your running pace or exercise intensity, past your VO2 max, must be fueled by anaerobic (without oxygen) energy sources.

The concept of VO2 max got its start back in the early 1920’s thanks to the efforts of two physiologists – A.V. Hill and Hartley Lupton. Hill and Lupton were the first to suggest that all energy came from either aerobic (with oxygen) or anaerobic (without oxygen) energy sources. Their ideas gave rise to the current popular theories of aerobic (with oxygen) and anaerobic energy production for runners.

Components of VO2 max

There are two principal physical components that determine your VO2 max

• A Big, Efficient Pump – First and foremost your VO2 max depends upon the ability of your cardiovascular system to deliver oxygen rich blood to your working muscles. High stroke volume (amount of blood moved through your heart with each beat), large, elastic veins and arteries capable of carrying the blood flow and a high maximal heart rate all contribute to an elevated VO2 max.
• Good Chemistry – Once the oxygenated blood reaches your muscles, they must be able to extract and use the oxygen to produce energy. Aerobic energy production takes place in structures called mitochondria in your muscle cells. A muscle that is more densely packed with mitochondria will be able to extract and use more oxygen. In addition to more mitochondria there are a number of muscle enzymes that help extract and use the oxygen. Both mitochondrial density and the availability of appropriate enzymes are increased through proper training.

VO2 max and Running Performance

In the past it was believed that VO2 max was the primary determining factor in running performance. Scientists and coaches in those days thought that a higher VO2 max translated directly to higher levels of running performance. Their thinking was logical – if you can process greater volumes of oxygen you should perform better as a runner. But, when statistics from elite runners were analyzed it appeared that it wasn’t that simple. When comparing the measured VO2 max of top level athletes to their running performances it was discovered that there was little correlation between VO2 max and performance.

As you can see from the above table there are large descrepancies between VO2 max and marathon finishing time. Among the listed athletes, Joan Benoit has the highest measured VO2 max but has the second slowest marathon time. It is obvious that VO2 max is not the only variable in running performance.

Today we know that VO2 max is only one contributing factor in running performance. Other factors include:

• Running Economy – How efficient you are at running has a huge influence on your running performance. If two athletes with identical VO2 max levels were to compete against each other, the runner who has the best running economy will be victorious because they are able to run faster while using less energy.
• Muscle Elasticity – This is a measure of how much energy your muscles will return. Your muscles are like big springs. During the stance or foot strike phase of your running stride your muscles eccentrically contract and store a lot of energy. A highly elastic muscle will store and return a high percentage of that energy during the push off phase of your stride. A more elastic muscle returns more energy and give your more power in your stride. You run easier and faster while using less energy.
• Running Strength - A strong muscle contracts with much more power and with more elasticity. This is the main reason that male runners have overall faster finishing times than their female counterparts despite the similarities in VO2 max.

Improving Your VO2 max

In the past, increasing training volume was the workout of choice for improving VO2 max. While that type of training does increase VO2 max, the most recent studies agree that high intensity interval training does the best job at elevating VO2 max. Genetics plays a role in your VO2 max but you can improve your VO2 max by up to 60% through training. Most increases in VO2 max takes place in the first 8 to 12 weeks of training.

Estimating Your VO2 max

The most accurate way to determine your VO2 max is through a laboratory test. While a lab test is the most accurate way it is also expensive and not a realistic option for most runners. You can estimate your VO2 max using your most recent race finishing times in the following table. If you have not completed any recent races do a 1 mile time trial on a track to estimate your VO2 max.

Keep in mind that for the same reasons VO2 max is a poor predictor of running performance, these estimates of VO2 max have some built in inaccuracies. But, this is a cheap and easy way to give you some idea of your VO2 max.