VO2 Max is an indicator of aerobic and cardiovascular fitness. Improving an individual’s fitness via cardiovascular exercise such as running can be measured by an increase in VO2 Max.
Although we often think of energy in terms of food and calories, breathing plays an essential role in helping our bodies to create the energy needed to move and run. We can miss a meal or two and suffer mild consequences, but if we fail to breathe for an extended period of time, we will most certainly die! Ingeniously, our brains are hardwired to regulate breathing. To create energy, we must breathe in Oxygen (O2) and exhale Carbon Dioxide (CO2). You may notice that while running, our bodies demand we breathe faster and deeper. This is because our leg muscle, for example, need more energy. To generate this energy, we needed to exchange O2 for CO2 at a faster rate to meet the needs of those muscles. This energy is used to generate the forces necessary for us to continue running! That’s right, our bodies are pretty darn smart.
So why does this matter? Well, a French exercise physiologist developed a test to measure how efficiently our bodies are able to consume oxygen, referred to as VO2 Max. Pronounced as “V-O-2-Max”, this is measured as the maximum rate that oxygen can be taken up during incremental exercise.
Imagine yourself gradually running faster, and faster, and faster, until … you can no longer carry on and must slow down or stop. During this process there is a specific point when your body was able to breath in oxygen and breath out CO2 at a maximal rate. It is this point that is referred to as VO2 Max, which reflects aerobic and cardiovascular fitness. When considering the example of running faster above, imagine another runner was able to run faster and longer than you could. While making several assumptions, this would suggest that they have a higher VO2 Max, and are more cardiovascularly fit. They can run faster and farther than you could because their bodies are more efficient at turning oxygen into running energy.
When we exercise, our muscles produce lactate, which is then converted to sugar for additional energy. When lactate is produced faster than it can be removed in the muscles, we reach our lactate threshold. Lactate threshold is reached more quickly with high intensity and endurance training. Regular training can raise your lactate threshold, and is a useful measure for desired running intensity. Interval and fartlek training allow our bodies to cyclically exceed the lactate threshold, followed by recovery.
Run Like a Prius
Let’s compare our bodies to automobiles. Firstly, our bodies and cars expel CO2 as a waste product of creating the energy needed to move. Unlike our bodies, cars use fossil fuels rather than oxygen as a source of energy. Secondly, some cars are more efficient at converting fuel into energy than others, allowing them to travel farther than less economical ones. The same is true for our bodies; some runners can run farther and faster partly due to how economically their bodies can take in oxygen and convert it to energy. Analogous to how many miles per gallon or litres per 100 kilometers a car gets for fuel economy, VO2 Max is an indicator of an individual’s running economy. If you drive a Hummer, it is very unlikely to improve fuel economy to that of a Prius. Fortunately, exercising in ways that tax our breathing, such as running regularly and employing different run types, will force our bodies to adapt to be more economical. This will be denoted by an increase is VO2 Max, representing an increase in aerobic and cardiovascular fitness.