Imagine you're an athlete playing your favorite sport. Your moment in the big game has come and the outcome now entirely hinges on your ability to reach deep and put out your peak performance. What does that mean for you?

If you are an athlete in excellent shape after years of conditioning with the daily support of the world's best trainers, you probably have a good idea of what your maximum effort can produce. But what if you're not and you find yourself in a situation where your athletic ability will be put to the test? Such a moment might come in the form of a friendly pickup game or just playing with your kids. Or it could come because you need to make a mad dash to catch your connecting flight at the airport before the gate closes. In all these situations, your fitness matters, so how fit are you really?

Most people don't have access to the top trainers and the equipment they use to bring professional athletes to the highest level of their performance. You may be surprised to learn you don't necessarily need that access to get a relatively good idea of how fit you really are.

What you need is an estimate of your VO₂ max, which according to Harvard Health, is "an objective measurement to tell just how fit you are". Here's how they describe the metric:

The V in VO₂ max stands for volume, while O₂ max stands for oxygen. As such, VO₂ max measures how much oxygen your body consumes while exercising. Typically, VO₂ max is measured as ml/kg/minute (milliliters of oxygen consumed per kilogram of body weight per minute of exercise).

When you breathe, your lungs absorb oxygen and transport it your red blood cells, which carry the oxygen to all of your body's organs and muscles. Your muscle cells need oxygen to generate adenosine triphosphate (ATP). ATP provides the main energy source your muscles need to do their work. The more oxygen you can breathe in, the more ATP your muscles produce, creating the energy to fuel your muscles and power your workout. (This is also why you breathe faster while exercising.)

If you have a higher VO₂ max, that means your heart and lungs are more effectively supplying blood to your muscles, and that your muscles are efficiently extracting and using oxygen from your blood. That's why a high VO₂ max is a good indicator of a high fitness level.

How high is your VO₂ max?

If you know a professional trainer who has access to an exercise medicine lab, they can hook you up to an apparatus that measures how much air you breathe while you engage in intense physical activity to get the best possible estimate of your VO₂ max. If you're like most of us, you don't have that access, but that's not a limitation.

That's because you can get a reasonable estimate of your VO₂ max by taking a very brisk walk on a relatively flat, mile-long path, a stopwatch, and a calculator. It wouldn't hurt to have a smart watch or other device that can measure your heart rate, but if you know how to take your pulse, you can get by with just a stopwatch or even a regular watch with a second hand.

What you'll do with those things is take the One-Mile Rockport Walking Test:

The one-mile walking test is an evaluation of cardiovascular fitness, that seeks to predict an individual’s aerobic capacity, which is also known as VO₂ max, or maximal oxygen consumption.

The one-mile walking test was developed by researchers in 1986 as an alternative assessment to accurately predict an individual’s aerobic capacity following a one-mile track walk. The test is both indirect and sub-maximal in nature, making it considerably easier to implement in field-based scenarios. While the test should be completed on a track or suitably flat terrain, it could reasonably be replicated on a treadmill.

The one-mile walking test is designed for both men and women aged 20-69 of varying levels of fitness. As the test only requires a participant to perform a brisk walk, it is also suitable for deconditioned participants, older adults, or those that are overweight.

Research conducted in 2011 found the one-mile walk test to be a valid predictor of VO2 max and a reliable alternative to the 1.5-mile run test that is widely used by the military.

Pretty impressive, right? HFE gives the following instructions to do it, which we've given a minor tweak:

• If available, attach the heart rate monitor and ensure that it is correctly measuring heart rate
• Start the stopwatch and commence walking
• Walk the planned route as quickly as possible without running or skipping
• Ensure that throughout the test, there is always 1-foot on the ground
• On completion of the distance, stop the clock and record the heart rate immediately

Our minor tweak is to the first step, where we added the words "if available". If you don't have a heart rate monitor available, take your pulse for fifteen seconds after completing the distance. You can then find your heart rate by multiplying the beats you count by four, which will determine your heart's beats-per-minute.

From here, you'll take your "as quick as possible" walking time for the mile, your heart's beats per minute at the end, your sex, your weight (in pounds), and your age and enter them in the following tool we built to use this information in a formula that will estimate your VO2 max. We've set the following tool up with some default data, please substitute your own data to get your results. If you're accessing this article on a site that republishes our RSS news feed, you may need to click through to our site to access a working version of the tool.

Once you have your results, compare them with the information in the following tables, which are also available at HFE's site:

The default data in the tool gives a VO₂ max value of 48.03 for our hypothetical 30-year-old, 180-pound man who walked one mile in 12 mintues and 15 seconds while their heart rate at the end clocked in at 164 beats per minute (which is what you would enter in the tool if you took your pulse for 15 seconds at the end of the walk, counted 41 beats, then multiplied this figure by four). According to the tables, our fast-walking test taker would be considered to be average in cardiovascular fitness for their age group (Age 21-30) and sex.

Remember to substitute your own data! Afterward, you will have a much better idea of how fit you really are. Best of all, you didn't have to strap on any strange breathing apparatus while hooked up to monitoring machines that go "beep"!

Image Credit: Person in white and black nike shoes photo by Sincerely Media on Unsplash.