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VO2 Max, Aerobic Energy, and Why it Matters to You

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You probably didn’t notice, but I recently made an update to the Level 1 fitness standards for Everyday Marksmen. The gist of the change is switching from a 1-mile running test to a 1.5-mile running test. That might seem like a bit of an arbitrary change, but I assure it was not. In this article, I want to talk about some of the things I’ve learned about aerobic fitness over the year, and how it influenced my decision.

Conditioning is your ability to produce energy to meet the task at hand.

Defining Conditioning

The definition of conditioning that K. Black puts in his Tactical Barbell II book is simple and to the point. We define well-conditioned as being able to execute a required activity while not being completely drained of energy.

The catch is defining the requirement. The energy demand is different for endurance runners than it is boxers. Likewise, it’s different for a mountaineer than it would be for someone engaged in small unit tactics individual movement. Ultimately, this is a question of specificity, but that doesn’t mean we should ignore the fitness aerobic base.

Human Energy Systems

Your body relies on molecules of adenosine triphosphate (ATP) to produce energy all over the body. ATP is integral to your muscles contracting, your heart beating, and even your brain thinking.

When your body uses a molecule of ATP, it breaks off one of the phosphates. This converts the ATP adenosine diposphate (ADP) and releases a bit of energy in the process. Your body uses the released energy for itself.

I’ll not go down the rabbit hole here, but understand that their are two primary systems your body uses to replenish ATP. One of them uses oxygen, the aerobic system, and the other does not- the anaerobic system.

The aerobic system relies on a combination of oxygen and some other fuel source, typically fat and glucose. It is generally slower, but is efficient and “burns clean” without producing much metabolic waste. This is your body’s preferred way to do business.

The anaerobic system has two stages, if you will. The first is the alactic stage, and it rapidly converts ADP back into ATP using Creatine-Phosphate stored in muscles. This system is extremely fast at producing ATP, but it only lasts about 10 to 20 seconds of intense activity before the Creatine-Phosphate stores are depleted.

The second, the lactic system, uses glucose to quickly produce ATP. However, the process without oxygen burns “dirty” and produces several metabolic waste products that your body then has to deal with. This produces a large stress on the body and increases fatigue.

In cave man days, dealing with these byproducts was a welcome alternative to dying because you couldn’t get away from that mountain lion. This is why the anaerobic system exists: to supplement needed energy for intense bursts of activity beyond your body’s normal aerobic capacity.

Putting it Together

With those definitions out of the way, know that both the aerobic and anaerobic systems are at play during activity. Your body does not turn off the aerobic system and switch over to anaerobic when things get to hard. Rather, the aerobic is always operating to provide energy to the demand. But when that demand exceeds your body’s ability to produce energy aerobically, as during sustained bouts of intense activity, then the anaerobic system kicks in to supplement the difference.

Even then, the anaerobic system can only go on for so long before the waste products begin to overwhelm the process. This happens in about 30-120 seconds of continuous maximum output, depending on the capacity of the individual. After that, power output decreases and your body forces you into a lower energy demand so it can recover.

In a somewhat poetic harmony, the aerobic system is responsible for dealing with those metabolic waste products. When they have been sufficiently dealt with, the anaerobic pathway becomes accessible again.

So to summarize, a strong aerobic capacity does two things for you. First, it allows your body to rely on the clean-burning energy source for a higher contribution of ATP as things become more intense, which means you feel less fatigue during an activity. Secondly, high aerobic capacity speeds up your ability to recover between bouts of highly intense activity.

What this Means for You

When you listen to long-time combat veterans, one of the things that comes up time and time again is fitness. Specifically the importance of “cardio” rather than strength. It took me a while to understand what they meant by “cardio.”

It’s not just long distance rucking over various terrain- though that is important. It’s also your ability to continuously get up, sprint a short distance, get down, and do it again over and over for hundreds of yards. If you don’t want to become a casualty because you were too slow, then you must be able to recover sufficiently between dashes in that brief lull you’re providing cover before the next dash.

In competition terms, think about some of the stages in the Brutality series or the Tactical Games. Such events always force you to exert some level of intense physical activity, like throwing a kettlebell and then sprinting after it before you take a shot. A stronger recovery ability means improving your chances to make hits. If you aren’t conditioned, then you might be sucking so much air that you can’t hold the rifle steady and your vision becomes blurred.

So Where does VO2 Max Fit In?

If we operate under the assumption that your aerobic capacity is your ability to efficiently utilize oxygen, then a proxy for that capacity is the Volume of Oxygen Maximum (VO2 Max).

VO2 max is a measure of milliliters of oxygen consumed per kilogram of body weight per minute. In practice, it’s a numerical value for how efficiently your body delivers and consumes the oxygen you breathe.

As an objective measure, it doesn’t account for age, sex, disability or any other factor. The number is what it is. Your VO2 max naturally changes over time, getting lower as you age. Women also have naturally lower VO2 maxes compared to men, but can still be quite capable.

Measuring VO2 Max

That brings me to the recent update to the Level 1 fitness test to use a 1.5 mile run. In 1968, Air Force researcher Major Kenneth Cooper (now called the father of aerobics), published a study about measuring VO2 max using a 12-minute run test.

The idea was to start a timer and measure how far someone was able to run in 12 minutes. The distance had a strong correlation to their laboratory-tested VO2 max. To administer it, the runner stayed on the inside-most lane of a standard 400-meter track and ran at a steady pace. The Air Force, being somewhat focused on scientific data rather than arbitrary measures (looking at you, Army 2-mile test), wanted to implement this measurement force-wide. The trouble was that it was too difficult to measure en masse with multiple runners and a single test administrator.

Dr. Cooper continued his research, and found that in lieu of a 12-minute test there was also a very strong correlation between VO2 max and how quickly a runner completed a distance of 1.5 miles. Cooper published his results, and the 1.5 Mile Run test was born, and continues to be used to this day.

The formula to estimate VO2 max from a 1.5 mile run is as follows:

VO2 max = (483/time in minutes) + 3.5

Putting it to Use in Our Fitness Test

Now that you know the source, let’s look at the scoring I’ve worked up for the Everyday Marksman Level 1 standards.

Unlike the military, someone’s results on our fitness assessment have no real impacts. Nobody is winning or losing a job if they run poorly, and nobody but the person in the mirror is going to care how you scored. So with that in mind, there is no scaling based on age or sex. The number is the number.

A perfect score on our 1.5 mile run requires a run time of 9:34. Using our formula, that’s an estimated VO2 max of 53.988, so effectively a 54.

“Excellent”, starting at 90 points in the test, requires a run time of 10:23, or a VO2 max of 50.

“Good” begins at 70 points and requires a run time of 12:00. That’s a VO2 max of 43.75. This should be your goal if you aren’t there already.

The bare minimum, or “Marginal,” requires a run time of 15:00. That’s a VO2 max of 35.7. Everything below that is poor by our standards.

These scores are not arbitrary. I looked at the various charts produced by Cooper and others to look for overlap between different age brackets. It’s not perfect, as Cooper’s charts get a lot more lenient between “good” and “excellent” as participants get older.

In general, I’d say that if your VO2 max is 45 or better, for an average person, you’re doing really well (That’s a run time of 11:37, by the way). Take a look at the Level 1 standards for the full breakdown on scoring.

Training Your VO2 Max

Now that you’ve seen the “why” and “what” of how I’ve incorporated VO2 max and the 1.5 mile run into our fitness standards, let’s briefly touch on how to improve yours.

The answer is not necessarily, “go run 1.5 miles a lot.” That’s the mentality I would have had 20 years ago.

Since the VO2 max is a combination of how well your body delivers oxygen (i.e. blood) to your body as well as how efficiently you use that oxygen, you need a two-pronged approach.

The first approach utilizes sustained low-intensity activity to strengthen your heart and blood vessels. This is the Maffetone-style training I’ve written about before. Keep your heart rate low. Roughly speaking, use 180 minus your age as your maximum. Aim for a range of 5-10 beats per minute below that and try to keep your heart rate there for at least 30 minutes. Do this 2-3 times per week to specifically improve your oxygen delivery.

To improve the metabolic efficiency side of the equation, the best method is high intensity intervals. That doesn’t have to be running or cardio, but any activity that provides sufficient energy stress for a short period. My personal favorite lately is circuits of 10 kettlebell swings followed by 10 burpees with a short 60-second rest. Another option is bouts of 60-90 seconds maximum effort rowing or cycling followed by a few minutes of rest.

This intense activity-recovery cycle teaches your body to manage its energy systems efficiently. Do this 2-3 times per week to improve upon your metabolic efficiency.

It’s difficult to effectively train both of these at the same time. So it’s best to periodize them over time. If you want to focus on the metabolic side, do 2-3 sessions of high intensity intervals per week and one session of endurance training just to maintain it. Keep this up for 8-12 weeks. Or, if your goal is the endurance side, flip it and do 2-3 sessions of low intensity cardio for at least 30 minutes and 1 session of high intensity intervals per week.

As an offshoot, there is also training for the Creatine-Phosphate process called alactic training. This has it’s own set of benefits, and the most direct way to do it is short bouts (about 10 seconds) of intense activity followed by rest. Think of an every-minute-on-the-minute (EMOM) workout where you do 10 kettlebell swings and then wait for the next minute to start.

Over time, your VO2 max will naturally increase and your run time will come down. You probably still need to keep running in the mix, since it’s a skill, but it doesn’t need to be the focus.

Of course, I’m not a doctor, nor an exercise physiologist, so take what I’m saying hear with a healthy dose of “bro science” salt. Check with your doctor before beginning any serious exercise program.

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Matt is the primary author and owner of The Everyday Marksman. He's a former military officer turned professional tech sector trainer. He's a lifelong learner, passionate outdoorsman, and steadfast supporter of firearms culture.

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Any thoughts on how to replicate the VO2 Max test with a rowing machine? 2500 meters maybe?


I like that you hit on anaerobic activity conducted at or near aerobic thresholds; burpees, eight count body-builders, kettlebell swings are great, as you mentioned. What about intervals as a replication of the movement that occurs in an advance or break contact scenario? Thanks!


Great in depth research for who – the ‘Everyday Marksman’? Sounds like ‘rucking’ and vigorous backpacking just isn’t going to cut it. Info great for those who ‘gym’ for numbers and live in an apartment vs. a farm or physical occupation. Throw a 40lb. pack on and go outside for a few miles – you’ll be better served. Just think this is ‘over done’….

Replying to  Matt

You’re right Matt. I just got caught up in the ‘numbers’ but modern exercise science is full of numbers isn’t it? I have always preferred getting exercise through application – like rucking vs. just running or obstacle courses vs. gym sessions (although without regular access to an obstacle course the weights in the gym had to do). Maybe I should find a ‘rock climbing’ gym? I must agree that all and any exercise is going to enhance one’s ability and on going research has given us the ability to ‘target’ those abilities with ‘specific’ exercise.

Replying to  Matt

I like playing golf too but it’s hardly applicable to a skill set required for a ‘Scenario X’ situation (unless you’re BAT21). I like to keep more serious training related to abilities that are likely to be required IMO – like rucking (bug out, patrol, recon) and general fitness through weight training and calisthenics (no obstacle courses in my AO!). I’ve found that the more ‘specific’ the skill – like marksmanship or strength training – the more effort must be made to maintain or improve that skill. It seems ‘priority’ plays a role here but we must have a foundation… Read more »

Old Combat Engineer
Old Combat Engineer

Agree strongly about the 1.5-mile in lieu of 1-mile run. Going back half a century to Dr. Kenneth Cooper’s “Aerobics” in ’68 and “Aerobics Program for Total Well-Being” in ’85, and which we were teaching at the Army Engineer School in the mid-1980s, we know that CV fitness begins to be measured by how far one can run in 12-minutes. For many younger people with reasonable fitness, that is about a 1.5-mile run. Glad to see that what we learned and taught then remains reliable.

Old Combat Engineer
Old Combat Engineer
Replying to  Matt

We were always looking to improve, Matt; but for a *standard* or to help develop a standard, it made good sense. And we taught it to the officers heading out to be troop commanders, who, in turn, required their soldiers to achieve at least that level of fitness. The 18th Airborne Corps–101st and 82nd–standard in the 1980s was 4-miles in 36-min: for us, at least, every Friday AM, wearing PT duds with running shoes. In ’77 GEN Blanchard required all of US Army–Europe to run 2-miles in 17-minutes–I mean everyone–females, too, any MOS–when we did all PT in combat boots.… Read more »

Replying to  Old Combat Engineer

I ran across an old Aerobics fitness book my sister had that was emphasizing a ‘running’ program with like ‘3’ maybe less exercises like sit ups, push ups and ‘air squats’. There were some standards to be met but they weren’t intense. Author insisted this was all that was necessary to maintain ‘optimum’ fitness. Does this sound like Cooper’s program? BTW – 1980’s USMC PT standards allowed a ‘passing grade’ in the 3-mile run at somewhere in the 24 minute area but most of us young ‘alpha males’ vigorously competed at the 18-19 minute level. Be interesting to see the… Read more »

Replying to  Matt

Right! Only Marine I personally knew who beat the 18 minute was our Senior Drill Instructor in boot camp. He was a slight built guy but a former 03 infantry grunt. He had the MCRD San Diego base record somewhere around 16 minutes. That’s fast! He’d start with us then he’d meet us (fully recovered) at the finish. It was almost discouraging! I will correct the 24 minute ‘pass time’ (8 minute pace isn’t bad) to somewhere around 28 minutes. I remember that because the PT score at the time was an accumulation of points between the run time, pull… Read more »

Replying to  Paul

To self -‘anaerobic, not ‘anabolic’ – idiot!

Old Combat Engineer
Old Combat Engineer
Replying to  Paul

Paul, I do not know if it was Cooper’s plan, since although he advocated other exercises to best maintain fitness, his focus was aerobic exercise. The fitness plan book did include recommendation of total body health, but if memory going onto 40 years is accurate, he had readers score their aerobic exercise in points, depending on time in the aerobic range. Was it maybe 30-points per week, minimum? Whatever, there was a clear prescription that guided out point tallies to ensure we did enough aerobic exercise each week. And, then, there was also the Army Run for Your Life (RFYL)… Read more »

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