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Why Aerobic Capacity Matters and How To Measure It

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aerobic capacity: woman jogging outside

It's true what they say — you cannot grow what you cannot measure. And aerobic capacity is the best way to measure gains made in cardiovascular fitness

In fitness, some things are more easily measured than others. In strength training, you can measure improvements in muscle mass or strength by tracking the circumference of various muscle groups, or by noting improvements in your bench press, squat, or deadlift

The same can be said for certain aerobic activities, such as running, biking, or swimming. You can watch your times improve in a 1600-meter run or a 800-meter swim, showing you're getting faster and more fit.

But for the average person — not a competitive runner or cyclist — it's hard to gauge improvements in aerobic training. Chances are, your workouts are a blend of HIIT training, endurance training, and resistance training (if you're following a well-balanced fitness program, that is). How can you measure any increases in fitness for these types of activities — beyond your own physical exertion? 

Your aerobic capacity is the best way to track improvements in cardio fitness. Below, I explain what aerobic capacity is, how it's calculated, and why it's an important measurement for any athlete.

What Is Aerobic Capacity?

In simplest terms, aerobic capacity is the maximum amount of oxygen you can consume at a high exercise intensity.

Here's how it works: When you perform any form of exercise, your lungs take in oxygen from the air you breathe. From the lungs, your body delivers oxygen to your bloodstream. From there, your heart and blood vessels move that oxygen to your skeletal muscles, allowing them to go to work. 

Aerobic capacity is a way to measure how efficiently the above scenario takes place. While there are a number of ways to measure aerobic capacity (more on this below), think of aerobic capacity as the volume of oxygen pumped through your body in a given amount of time

While a number of genetic factors can influence your aerobic capacity — age, gender, and bodyweight — it's also directly correlated with your cardiovascular fitness level. If you start a regular exercise program, your overall oxygen consumption (and efficiency) will increase. In other words, the faster, and more efficiently you can pump oxygen through your body, the more capable your body will be at handling high-intensity exercise. 

Why Should I Care About Aerobic Capacity

aerobic capacity: woman doing a jump rope at home

If you're wondering, "But why do I care how much oxygen I consume...?" hear me out: Aerobic capacity is another way to measure — and therefore track — your aerobic fitness level. As you increase your degree of fitness, you will be able to use oxygen much more efficiently, thereby improving your aerobic capacity.

The first time you ran 1,600 meters (1 mile). Whether you were an elementary kid in gym class or an adult training for your first 5K, chances are you heaved gasps of air throughout your entire run.

However, if you kept running — or performing another form of cardiovascular workouts — for several weeks, months, or longer, you probably noticed your lungs didn't have to work as hard. In fact, after weeks of training, you probably had to run much further (e.g., a 5K) or faster (e.g., sprint intervals) to pump the same amount of oxygen through your lungs.

Knowing your aerobic capacity is valuable because it helps you gauge improvements in your cardio fitness level. If you have a low aerobic capacity, it can also be used to determine whether you are at risk of developing heart disease, high blood pressure (hypertension), or other risk factors. 

With anaerobic exercise (i.e., resistance training), you can track improvements through increases in strength, such as kilos lifted. However, unless you're timing yourself running on a track, it's difficult to note improvements in recreational aerobic exercise, such as HIIT workouts.

Is Aerobic Capacity the Same as VO2 Max?


Aerobic capacity and VO2 max are often used interchangeably. You may also hear aerobic capacity described as aerobic power, functional aerobic capacity (or functional capacity), or maximal oxygen uptake

Your VO2 max measures your aerobic capacity in the milliliters of oxygen you consume per minute. In a VO2 max test, you'll be hooked up to an oxygen mask in a laboratory, placed on a treadmill, and forced to run as fast as you can. Your VO2 max occurs when you physically can't pump oxygen any faster. Therefore, it helps you gauge your maximum effort under competitive conditions. Olympic and endurance athletes often measure their VO2 max to understand their true max effort — i.e., how fast they're capable of running. 

How Can You Measure Aerobic Capacity?

While aerobic capacity is considered the gold standard in understanding your cardiorespiratory fitness level, it can be difficult to measure. As you just learned, understanding your true VO2 max (one measure of aerobic capacity) will take place in a lab — which isn't feasible for the average person. 

Therefore, if you're not looking to run in the Olympics, but just want to better understand your fitness level, there are a couple ways to estimate or measure your aerobic capacity

1. Fitness Wearables 

Fitness wearables, like Garmin, Fitbit, WHOOP (use my link and we both get one month of WHOOP for free), and other smart watches, often include VO2 max as one of their measurements. While this offers an easy, affordable way to track your aerobic capacity, know that these measurements are only estimates.

Wearables typically use your height, weight, heart rate, and age to calculate your aerobic capacity. Since it has no way of measuring the actual volume of oxygen being pumped through your body, this is the least accurate method, but can be used as a baseline.

2. Online Calculators 

There are a number of online calculators that can help you gauge your aerobic capacity. Omni Calculator, for instance, has you measure your pulse rate for 15 seconds after performing a number of physical activity tests (stepping, walking, running, and rowing). 

Like wearable watches, online calculators are easily and accessible to the average person — however, I approach these numbers with caution. The point of calculating your aerobic capacity is to understand what your body is truly capable of — which frankly, won't be tested through low intensity exercise (e.g., walking for 3 minutes). 

3. Calculate VO2 Max By Hand 

To calculate your VO2 max the old-fashioned way, you will need to measure your resting heart rate and your maximum heart rate:

  • Resting heart rate (RHR): Take your pulse, calculating the number of heart beats in 20 seconds. Multiply by three.
  • Maximum heart rate (MHR): To calculate your maximum heart rate, you will need to exhaust yourself physically. To do this, try running eight 100-meter sprints at 100% effort. Or, you could try performing ten 30-second sprints on a stationary bike at 100% effort. After your last interval, immediately take your pulse for 20 seconds. Multiply the number of heart beats by three.

Your VO2 max = 15.3 x (MHR/RHR). For example, if your maximum heart rate is 220 and your resting heart rate is 66, your VO2 max would be 51. 

Here are typical VO2 max fitness scores for men by age:

aerobic capacity: graphic table of typical VO2 max fitness scores for men by age

And here are typical VO2 max fitness scores for women by age:

graphic table of typical VO2 max fitness scores for women by age

Images: Garmin blog 

4. The Cooper Test 

The Cooper Test has been used by the U.S. Air Force for 50 years to understand maximal exercise exertion. When results of the Cooper Test are compared with laboratory VO2 max tests, it shows a correlation of 0.897 (science says a true correlation equals 1.0, so a nearly 0.9 correlation shows the Cooper Test is highly accurate). 

To perform the Cooper Test, you'll run for 12 minutes on a fairly flat surface (such as a track), under good weather conditions (no wind or precipitation). You'll need to ensure you warm up and are properly hydrated before taking the test.

At the end of 12 minutes, calculate how far you ran in miles. Enter your age, gender, and distance run into this online calculator to calculate your results. 

Tips To Improve Aerobic Capacity 

Now that you understand aerobic capacity and how it’s measured, you’re probably wondering, “How do I improve aerobic capacity?”

Running 5 kilometers day after day will not help improve your aerobic capacity. Instead, I encourage you to challenge your body in different ways, including: 

  • Set a goal: After you understand your baseline for aerobic capacity, set yourself an attainable goal. How do you wish to improve over the course of three months, six months, or longer?
  • Be consistent: To reach a goal, you need to be consistent. Following a balanced plan will help you be consistent in your workouts.
  • Watch your nutrition intake: Following a balanced diet can help improve your aerobic capacity. 
  • Practice progress overload: Tweak your sets, reps, and resistance to increasingly challenge the body. In addition, try adding a source of source of instability or try single-leg or single-arm movements to challenge the body in new ways.
  • Make everyday habit changes: Try to move more throughout the day to increase aerobic capacity. Bike to the grocery store, walk during your lunch break, and try using a standing desk at work.
  • Measure your progress: Continuously re-test your aerobic capacity so you can make modifications to your wellness routine as needed.

Track Your Aerobic Capacity To Measure Cardiovascular Improvements 

woman tying her shoelace

A well-balanced fitness program, like Build Bullet-Proof Health, blends cardio- and strength-based workouts, while making proper nutrition and recovery a priority.

Unfortunately, it's far easier to measure gains in muscular strength versus gains in cardiovascular training. To track how HIIT and other cardio workouts increase your fitness level, measure your aerobic capacity. You can measure your aerobic capacity at home, online, or in laboratory exercise testing.

Tracking your progress is the best way to achieve your goals. To discuss your goals one-on-one, sign up for the premium membership of Build Bullet-Proof Health. Each month, you'll get virtual meetings with me, where we can discuss your progress.

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