The first post of the Endurance Performance Series introduced the “holy trinity” of endurance performance: VO2max, lactate threshold and economy. Together, these three components are the foundation of endurance performance. Today, we will take a closer look at the most central of these components: VO2 max.
What is VO2 max?
VO2max refers to the maximal rate of oxygen consumption during exercise. Despite the fact that the actual lab measurement (maximal oxygen uptake) does not matter in itself, the implications are extremely important. By measuring the maximal oxygen uptake of an athlete (usually in mL of O2 per minute per kg body weight), we can calculate the maximal rate of aerobic energy production possible in the athlete’s muscles. Knowing the upper limit of the aerobic energy system gives important information regarding maximum performance potential as well as critical training prescription guidance.
What Determines VO2max?
The VO2max of an athlete is the culmination of different systems in the body working together to achieve the end goal of meeting energy demand. In the end, the body is trying to provide working muscles with oxygen. To do so, oxygen is taken from the air and diffuses into the lungs. From the lungs the oxygen must diffuse into the blood. Once oxygen reaches the blood, the heart must pump this oxygen-rich blood around the body to the working muscles where the oxygen is then taken up by the mitochondria and used for aerobic respiration.
This process is typically broken down into two systems; the central system (heart) and peripheral system (lungs). Over the years, several studies have highlighted the importance of the central and peripheral systems and have concluded that the primary rate-limiter of oxygen transport is the heart’s ability to pump blood (in well trained endurance athletes). Why? When isolated, human mitochondria are able to uptake and use far more oxygen than any human heart can provide. Therefore, the more blood that the heart can transport, the greater the energy demand the mitochondria can meet.
How to Test VO2max
For me, there are three valuable ways to test VO2max. The most accurate way to test your VO2max is in a lab with a metabolic cart. The cart actually measures your peak oxygen consumption and is the gold standard when it comes to VO2max measurements. This test will also let you know what your power/pace at VO2max is.
A second way to estimate VO2max is with a 5 minute power test. Although this test gives no direct metabolic data, 5’ max power correlates very closely with power at VO2max and can be easily tested over time. This is a cheap, practical and useful way to estimate your power at VO2max. In a later post, I will cover how to calculate an estimate of VO2max (in mL/min/kg) using only power data.
Finally, software like that provided by INSCYD or Aerotune uses power data to estimate VO2max and power at VO2max. This can be done by hand (like mentioned above) or you can rely on the software.
How to Use VO2max in your Training
Knowing your own VO2max can be helpful in three primary ways. First, the VO2max is the ceiling of aerobic energy production. Knowing the ceiling allows you to calculate the ideal amount of work (in kJ) to be done over time to induce the best training response (mitochondrial proliferation and function). This is thanks to the work of Alois Mader and will be covered in an upcoming post.
Second, knowing the power/pace at VO2max allows you to put all training intensities into the context of your own maximal aerobic power. Unlike using FTP/threshold as the cornerstone power/pace value, using % VO2max to gauge your exercise intensity allows you to more accurately understand how intensely different powers/paces are stressing your aerobic system.
Finally, using maximal aerobic power/pace as a reference for all other intensities - mainly LT1 and LT2 - gives you critical insight into how much of your VO2max is “accessible” for extended periods of time. This information is invaluable when it comes to deciding on what kind of training to focus on and will be covered in depth in the upcoming post on lactate threshold.
How to Improve VO2max
Remembering that VO2max is primarily determined by stroke volume and mitochondrial density, training that increases these parameters is likely to be the most effective for increasing VO2max. To increase stroke volume, strength of the heart must be increased. To do this, you can focus on accumulating many, many beats of the heart over time. For lesser trained athletes, maximal stroke volume is achieved at a low intensity. Therefore, focusing on low intensity training is likely the best route for non-elite athletes and is also necessary for adaptations in elite athletes. For elite athletes, high intensity interval training (HIIT) is an effective way to increase VO2max/power at VO2max. Studies by Ronnestad show clear correlations between HIIT programs and increase in stroke volume/VO2max. Intervals like 30/30, 30/15, 40/20 tend to result in the largest improvements in VO2max in elite athletes.
Summary
To summarize, VO2max refers to an athlete’s maximal aerobic power. The primary driver of VO2max is stroke volume, with mitochondrial density also playing an important role. There are several ways to test VO2max, including lab testing and field testing. Finally, doing extensive easy training combined with HIIT is a potent stimulus to increase VO2max.
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