top of page
  • Writer's pictureTyler

Fitness Testing: Part 3 | VO2 Max Test

Updated: Jun 7, 2023

What's your aerobic threshold? Learn more about why a VO2 Max test can help you optimize your workouts and improve your cardiovascular fitness.



After I finished the DEXA Scan and RMR test, the third and final item on the agenda at Live Lean RX was the VO2 Max test. The VO2 Max is usually conducted on a treadmill or bike and is designed to provide you with data on how effectively you consume oxygen during exercise. This is the gold-standard test of endurance and the best way to accurately determine your aerobic fitness and efficiency. It measures your different heart rate zones, your caloric burn at each level, and how this output compares to other people of your age and gender. Whether you are a weekend warrior or an Olympian, these metrics provide tremendous insight into your body, allowing you to craft a more effective training program to improve your cardiovascular health.


The Test:

VO2 Max Test

Determining your maximum oxygen consumption ability requires working through your full heart rate (HR) range until you have hit your ceiling, while simultaneously recording the results. This process usually takes about 6-8 minutes, depending on fitness level. I completed my test on a treadmill while hooked up to a HR monitor and with a breathing tube strapped to my face, both of which were connected to a computer. As with any "maximum" test, there is certainly some discomfort involved as you push to your limit, and running with tubes attached to your face certainly doesn’t make it any easier.

The test began with the treadmill set at a slight incline and a speed-walking pace. The speed then increased every minute, with my rising HR quickly becoming a distraction from the awkwardness of running with an apparatus strapped to my face. Before I knew it the 8 minutes was up, I had hit my maximum and was able to stop and take a breather.



Before diving into the results, I want to cover some definitions that will be necessary to interpret the numbers. The primary focus will be on the difference between aerobic and anaerobic activity because I believe that is the most actionable data this test provides. A disclaimer, once again, I do not have formal training in physiology or nutrition. These are complex concepts, and I am only presenting my interpretation from the research I have done.

Aerobic vs. Anaerobic

The aerobic zone is one where your heart rate level is at or below your "all day" pace, generally described as an output you could sustain for longer than 120 minutes. It is also colloquially known as your "fat burning zone." Your aerobic threshold is the upper limit of this zone, a term that will come up again later.

If your heart rate goes above this threshold, you move into the anaerobic zone, an output that can only be sustained for short durations due to its intensity. The primary difference between aerobic and anaerobic activities is related to the type of the fuel your body burns changing at the different intensities. I am not an expert in this subject, but knowing these basics is a must for anyone who puts a lot of time and effort into their fitness, so bear with me. Below is a very simplified description of those fuel sources.

Energy Systems

The energy in your cells is provided by a substance known as Adenosine Triphosphate (ATP), which can be created by three different biochemical processes.

Exercise APT Systems

Phosphagen System | The first process is via the phosphagen system, which creates creatine phosphate. This is the fastest way for the body to generate usable ATP, and it is a powerful source of energy for muscle movement. Although the muscles can only store small quantities at any given time, it is critical for explosive and instant response, and it is the reason why creatine supplementation is recommended for almost all athletes. During periods of very high exertion, your body usually burns this fuel up in about 8-10 seconds. This is the red line on the chart referred to at ATP-PC.

Glycolytic System | The second process is via the glycogen-lactic acid system, which produces ATP using complex carbohydrates called glycogen. Glycogen is converted to glucose (sugar), which is then converted into ATP, and as a byproduct creates lactic acid or lactate. The buildup of lactic acid causes that familiar burning sensation that you feel in a muscle when you are pushing the intensity. While not as rapidly available as the phosphagen system, this process allows the body to produce ATP without oxygen, hence the term anaerobic or "without air." This fuels the muscles for high output efforts under 90-120 minutes in duration. Given the standard American diet is high in carbohydrates and workout duration is usually under 90 minutes, this is the primary fuel source most athletes use during exercise.

Oxidative System | The third process is called the Oxidative System, or Aerobic system. Aerobic meaning "involving or requiring oxygen." When you are below your aerobic threshold, your body is able to break down fatty acids from fat stores for fuel by utilizing oxygen to create ATP. Due to the need to transport oxygen to the muscles first, it is a much slower process than the other systems. This is the type of energy used for longer duration, lower intensity endurance events due to the abundance of fuel available in the body. A pound of fat contains roughly 3500 calories, thus even people with a low body fat percentage are carrying tens of thousands of calories worth of stored energy that can be used.

The chart below provides a concise comparison of the systems.

Exercise Fuel Sources

VO2 Max | Finally, it would be an oversight not to discuss what VO2 Max actually is, given that it’s the name of the test. VO2 Max simply means the maximum volume of oxygen (VO2) that your body is able to process when you are pushing it to 100% capacity. Unless you are doing very high level endurance training, I don't think it’s necessary to understand all of the technical details behind the number, but having an unbiased measure of your fitness to compare to your cohort is certainly a valuable benchmark.



As is true with all of these tests, there is value in the data to know where you stand, but the real benefits come with how you apply that knowledge. In my case, while it is interesting to know my VO2 Max (38.2) and get a better sense of my fitness, given my goal at this time is fat loss, I am not too concerned that it is only in the “fair” category.

Vo2 Max chart
VO2 Max for Males by Age

The number I was most interested in learning from this test was my aerobic threshold. That’s because to have success in a fat loss plan, you need to make sure your workouts are actually helping you burn fat! Knowing where my fat burning zone ends will help make sure my workouts are optimized to pull from this fuel source.

Sadly, burning fat isn't as simple as staying in your aerobic HR zone. Your body burns your easily accessible fuel (glycogen & APT-PC) first, and only when that is depleted will it transition to burning fat for fuel. This is why many people have success with the Keto/low carb diet; by not replenishing your body with carbs, you are forced to start burning fat as fuel sooner. With this understanding, my plan is to begin my workouts by doing some HIIT or strength training, which deplete glycogen quicker, and follow that up with long, steady-state cardio in my aerobic zone. Exercising in this order while in a caloric deficit should help me start burning fat sooner to maximize my results, without having to do 90+ minutes on the bike every day.

Beyond potential fat loss, there are also many other health benefits associated with exercising in your aerobic zone that relate to your base level fitness and mitochondrial function. If you are interested in learning more about those benefits, listen to this Dr. Peter Attia podcast with Iñigo San Millán for a deep dive.



Dieting and fat loss is not a fun process for anyone, and taking steps to work smarter rather than harder needs to be part of the plan to increase your chances of success. With the information gleaned from this test, I can be confident that I am getting the most bang for my buck out of my exercise by eliciting a specific response from my body. Crafting a more targeted approach should yield quicker and more effective results as I work toward my goal. As always, I look forward to using this data to help motivate me, and I am excited to take another test in a few months to see how things have changed.

To wrap things up, if you are an endurance athlete looking to optimize your training, I believe there is tremendous value in taking this test to learn your heart rate zones. It will bring clarity and efficiency to your training that simply isn't possible without this data. For those who are less conditioned or not working toward endurance goals, this level of granularity might not be worth the cost (about $100). Instead, just focus on increasing your activity and good things will follow.



215 views0 comments

Recent Posts

See All


bottom of page