There is no doubt that improving diet is a powerful way to shift metabolism and reverse conditions like insulin resistance and chronic inflammation.  In fact, in my early days, simply changing the diet in patients led to such significant changes in metrics like body weight, triglycerides and glucose, that patients often thought exercise could be optional or done far less frequently.

The HIIT (high intensity interval training) movement also sent a message that very short bursts of exercise could replace longer aerobic sessions and an emphasis on weight training led to many patients doing weights instead of, rather than in addition to cardio workouts.

Fast forward to today and I’ve noticed an interesting phenomenon as I have aged along with my patients.

Many of my patients who initially had significant improvements in body weight, glucose and cholesterol, who did not exercise much, all of a sudden after a few years are seeing a recurrence in their health issues despite adhering diligently to diet.

Waistlines and lab numbers are creeping up and even feelings of fatigue are starting to arise.

Even I made the mistake several years ago of spending more of my workout time doing weight training and HIIT sessions, and scaling back on prolonged cardio.  What did I notice as a result?  My lab numbers did get mildly worse, but more significant was that my endurance for longer runs and basketball games took a major hit.  In other words, I became gradually aerobically conditioned over time.

In this post, I’m going to dig a little deeper into the science of aerobic fitness by discussing a marker called VO2 max.  The goal of the post is not for everyone to go out and get a VO2 Max test done, but rather to use this measure to deepen your understanding of aerobic fitness and why it is one of the most important indicators of heart disease risk, longevity, and quality of life.  When my patients improve aerobic fitness the RIGHT WAY, they avoid injury and notice the most significant improvements in energy and mood that no medication or supplement can provide.

If aerobic training is done incorrectly, like most of my patients before seeing me, aerobic fitness stalls or gets worse and leads to hunger and dietary patterns that may actually increase disease risk.  I have lost track of how many of my patients had a heart attack or some other chronic health condition despite regularly performing what they thought was a proper aerobic or cardio routine.

Now before you start reading this post, I want you to know that I will be getting into some scientific details when discussing VO2 max, but if you hang in there, I will provide very practical information at the end that allows you to monitor your baseline and follow-up aerobic endurance levels during your preferred activities (walking, running, cycling, rowing, etc.).  I also include a very important section on children’s health given my grave concern for the deteriorating aerobic fitness status of kids and adolescents today.  Please be sure to read this post to the end and if the VO2 max section is too scientific for you, skip it and go to the sections that follow for practical recommendations for adults and children.

Your aerobic fitness is arguably the single most important metric defining your risk of disease, your fitness, your energy, and your longevity, yet so many people have little to no understanding of how to quantify this key measure.

Get to Know Your Mitochondria

Mitochondria are tiny power generating units inside our cells that convert food and oxygen into energy molecules called ATP (adenosine triphosphate).  To keep things simple here, if you are a car, the mitochondria collectively are your engines.  A quantitative reduction in your mitochondria means you have fewer numbers of mitochondrial engines, while a qualitative impairment means the actual engines are damaged and cannot adequately produce sufficient ATP energy output.

Damaged mitochondria are not just insufficient energy generators.  They also generate environmental pollutants called free radicals which can cause further damage and increase the risk of common health conditions like cancer, heart disease, and Alzheimer’s disease.  Again, the car engine analogy works perfectly here.  If you don’t take care of your car (body), the damaged engine (mitochondria) will compromise performance and produce pollutants (free radicals).

Together I refer to both of these states with a term I coined called “Mitopenia.”  The “penia” suffix refers to a reduction or deterioration, such as the condition called sarcopenia which is age or disease-related muscle loss.  Mitopenia can be thought of as a microscopic or molecular version of sarcopenia when it affects the muscle cells.  Mitochondrial degeneration in other types of cells are linked to a whole host of different chronic health conditions.

There are no simple blood markers of mitochondrial function yet, that are easily accessible in a clinical setting.  This is where VO2 max and aerobic function come in, which we’ll discuss next.

What’s VO2 Max and Why It Matters?

I’m neither a mechanic or a car enthusiast, so I will continue to make car and engine analogies throughout this post which may not be necessarily accurate, but hopefully illustrative and instructive.  When we think of how fast or powerful a car is, we often refer to the letter “V” followed by a number, which refers to the number of cylinders the engine has for fuel intake.  For example a V8 engine in a given car would be considered to be more powerful than a V6 engine. By the way the “V” designation comes from the fact that the cylinders within the engine actually make a visual V-shape like in the image below.

V engine like mitochondria
V-line Engine

There are clearly other performance indicators as well which can make one brand of a V6 sports car much faster than the V8 engine of another brand, but again we are using this as a model to understand mitochondrial performance.  Some of you might be thinking, why don’t I just use “horsepower” as the analogy, but I’m choosing the V-line since the “V” nicely connects to VO2 max which we’ll discuss next.

Until we have a more easily measurable way for determining mitochondrial function and performance, VO2 max, a measure of aerobic performance, will have to suffice.  VO2 max refers to the maximum volume of oxygen an individual consumes and utilizes during exercise.  It’s not just how much oxygen you breathe in through your mouth, but also how much is removed from your blood to enter the mitochondria in your cells to help fuel the conversion of nutrients into energy.  To put it more bluntly, the oxygen from the air your breathe combines with carbon atoms from the food you eat to procreate inside your mitochondria to produce high energy offspring molecules called ATP.  How’s that for a memorable visual?

This again works beautifully with the car analogy because a car with more cylinders (a V8 vs a V6 engine) or more horsepower has the ability to take in and utilize more fuel to convert to energy so it can race down a highway at greater speeds, while a human being with a greater VO2 max also has greater capacity to consume and utilize more oxygen (and carbon) fuel during exercise so she can run further and faster.

Other than the ability to increase your ability to exercise longer and harder, VO2 max is an important marker for longevity and disease risk.  My clinical work is focused on preventing and reversing insulin resistance, the root cause of most cases of diabetes, obesity, heart disease and many other chronic health conditions.  There is a strong correlation between VO2 max and insulin resistance.

This makes perfect sense because as we mentioned earlier, VO2 max is a marker for mitochondrial function and if the mitochondria in let’s say your muscle cells are damaged, then your muscles can’t remove glucose from the bloodstream, which leads to elevated blood sugar and diabetes over time.  Watch the video excerpt from my program below which highlights how the muscles clear glucose from the bloodstream after exercise.

Aerobically unfit individuals who have a low VO2 max have defective and deconditioned mitochondria that cannot efficiently clear glucose from their blood after meals or even after exercise.  In addition, parents who have insulin resistance have children who have greater impairments in ATP energy production and VO2 max.

For parents reading this post where either or both have insulin resistance, you had better make sure your children stay physically active and do almost daily aerobic exercise to prevent future disease.

Refer to the Children’s section later in this post.  For those planning to get pregnant, I strongly suggest both parents improve their diet and increase aerobic fitness so they don’t increase the risk of mitochondrial disease and insulin resistance in their future children.

If you would like to hear a more in depth discussion about the relationship between VO2 max and insulin resistance in adults and children, listen to my podcast appearance on Dr.Peter Attia’s The Drive here where we discuss this very topic at the 59 minute mark.

Measuring VO2 Max

How is VO2 max actually measured and what do the numbers mean?  Before I get into this, I want to warn some of you that I will get a little bit detailed with the science in this section because I think it’s important.  Don’t give up on this post though if I lose you here.  Please read the subsequent sections which will provide other really important and more accessible measures of aerobic and mitochondrial fitness that nearly anyone can understand and measure.  Now back to VO2 max.

I got my first VO2 max test done as an undergrad at UCLA where I was an exercise physiology major and then got a more recent test done before writing this post.  Coming back to cars, while I was getting set up to do my VO2 max test, I realized that the process looked oddly similar to my car getting a smog check at the local gas station.

During a smog check, your car is driven up to a platform, a sensor is placed inside the exhaust pipe as shown in the image below, and then the tailpipe emissions are measured by a computerized device.  The five gases monitored during a smog check are Hydrocarbons (HC), Carbon Monoxide (CO), Nitrogen Oxides (NOx), Carbon Dioxide (CO2), and Oxygen (O2).

smog check analogy to VO2 max test
Smog Check-VO2 Max Analogy

During my VO2 max test, I was put on a treadmill, also hooked up to a computer, and then asked to progressively increase my exercise intensity, similar to revving up my car engine during a smog check, while wearing a tight fitting mask.  My mouth is analogous to the tailpipe of the car pictured above and the emissions being measured were CO2 and oxygen.

VO2 Max testing
My VO2 Max “Smog Test”

In the initial phases of exercise when your intensity is being slowly ramped up, you are mainly in aerobic metabolism, where oxygen is being used at increasing rates as your body’s energy demand increases.  How hard you are working on the treadmill is marked by your heart rate.  At a certain point the rate of oxygen you consume actually plateaus even though your exercise intensity and thus your heart rate continues to increase.   This plateau point is your VO2 max.

Now as I continue to exercise harder and faster beyond my VO2 max, where does my energy come from?  It comes from anaerobic (aka “without oxygen”) metabolism with a process called glycolysis, which relies on glucose, not oxygen, as the primary fuel source to produce ATP energy.  This anaerobic metabolism does not take place in the mitochondria, but instead in a region of the cell called the cytoplasm.  Back to cars, let’s use the hybrid analogy.  I am a hybrid vehicle and would prefer to use electric (fat) energy over gas (glucose) energy, because burning fat energy means losing more body fat and having the ability to exercise longer.

During lower intensity exercise like the casual warm-up walk in the image above, I am almost exclusively in electric fat burning mode, but the amount of fat I’m burning is not great because my intensity (marked by heart rate) is within the lower end of the fat-burning aerobic zone.  As my exercise intensity and heart rate go up, I will continue burning mostly fat until I exceed my aerobic capacity and then switch over to anaerobic metabolism.  That point is often called the Crossover Point (COP) or Aerobic Threshold (AT).

If my COP or AT is at a heart rate of let’s say 130, then as my heart rate exceeds 130, I start burning a greater amount of glucose and a lower percentage of fat.  Working out way above your COP puts you in the red zone of your RPMs which might be good for short periods of time, but if most of your workout are in the red zone, you are going to burn your engine/body out and increase your risk of injury.

The vast majority of patients I see in the clinic have absolutely no awareness that their walks, runs, rides, etc. are mostly in the red zone.

Unlike a car where you can clearly see the RPM meter getting into the red zone and you hear the loud engine sound, most everyday exercisers who think they are working out in the aerobic zone are actually in the red zone.

RPM Meter similar to HR zones
RPM Meter

Think of your heart rate as being analogous to your RPM meter.  For a car, RPM stands for revolutions per minute, which is how fast your engine is spinning.  Your body’s RPMs are actually measured as BPMs (beats per minute) represented by your heart rate.

Your goal during most of your workouts is to push your heart rate as close to the red zone as possible, without actually entering the red zone.

The heart rate zone chart below might be familiar to you since it’s posted in most gyms.  The way you calculate your heart rate zone is as follows:

  1. Calculate your maximum heart rate (MHR) by subtracting your age from 220.  Let’s pretend your 40 years old, so your MHR would be 180 (220-40).
  2. Now use the percentages in the chart to find your target zone.  I’ve emphasized the aerobic zone which is 60-80% of your MHR, which would be a heart rate between 108-144 beats per minute (bpm).
Heart Rate Zone Chart
Heart Rate Zone Chart

In the above example of the 40-year-old, after warming up, you would want to exercise at a heart rate as close to 144 as possible.  I discuss aerobic vs anaerobic metabolism in the context of exercise in this post.  I also explain in that post what I think is a simpler and more elegant way to estimate your maximum aerobic heart rate which is 180 minus your age.

So for our 40-year-old, that would be 140 and for individuals who are fit and don’t have significant underlying health issues, you can add 5 points.  That would mean 145 for this individual which is pretty darn close to the other calculation we did.  This formula is the Maffetone or “MAF” heart rate which I explain in further detail in my post or you can also read about at Phil Maffetone’s site here.  I also did a podcast interview with Dr.Maffetone himself which I strongly recommend you listen to here.

Now when people say I’m going to go “burn off all that fat” from yesterday’s binge eating episode, they typically exercise at an intensity that is not maximizing the burning of fat.  Instead it’s burning a higher proportion of glucose.  When you are huffing and puffing through your mouth during a run or a cardio class, the heavy breathing means you have essentially run out of oxygen.  Remember oxygen is necessary to fuel body fat-burning aerobic metabolism.  You’ve now switched over to a predominantly glucose, rather than fat-burning anaerobic metabolism.

You may be burning more overall calories with your intense workout, but the sad news is that very little of those burned calories are coming from body fat.

You are exercising in the highly inflammatory red zone, which increases your risk of injury, fatigue, and intense sugar cravings since that is your predominant fuel source during your workouts.

One last technical point for those of you who are following along with the science here.  How does the VO2 max test actually estimate how much glucose and fat you are burning?  Since we can measure how much oxygen is being consumed and how much CO2 is being released during exercise, and we know the equation for how much oxygen it takes to burn a single carbohydrate (glucose) and fatty acid (fat) molecule, we can use some simple chemistry and math to determine how much glucose and fat you are burning based on a ratio called the respiratory exchange ratio or RER.  I can cover this in more detail in a separate post or you can read a bit about it here.

Other Markers of VO2 Max

As I mentioned in the beginning of this post, I’m not expecting everyone to go out and get a VO2 max test done, although it is getting more accessible through medical centers and even gyms that are offering this test to measure baseline and follow-up numbers after specific training protocols.  This approach has been a training standard for elite endurance athletes, but is now creeping into the recreational athletic world so amateurs like me can perform better.

I like this trend because for athletes VO2 max measurements help them perform better during a race, while for the rest of us non-athletes these improving VO2 max help us exercise and play better, while also reducing disease risk and improving mood and energy.  Remember, VO2 max is a measure of mitochondrial function and mitochondrial function is a measure of overall heath and disease risk.  If you can’t easily get a VO2 max test done, there are other ways for you to assess aerobic function which I’ll list off below.  Remember that we are using aerobic function as a surrogate marker for mitochondrial function and overall health.

Despite so many of my patients obsessing over their body weight, cholesterol, blood sugar, and/or blood pressure, their aerobic function is the singular metric that has the greatest correlation with heart disease and overall chronic disease risk, longevity, energy, and quality of life.

You need to know what your current level of aerobic function is and then periodically assess it to track improvement over time.  In order to assess your aerobic fitness levels, the 3 key metrics you need to measure are the following:

1. Distance:  How far are you walking, running, cycling, rowing, etc.?

2. Time:  How long did it take you to cover a given distance?  For example, it took you 10 minutes to jog 1 mile.

3. Heart Rate:  Your heart rate is a measure of your exercise effort and also marks the transition zone we discussed earlier where you go from burning predominantly fat (aerobic exercise) to predominantly glucose (anaerobic exercise).

The good news about the above 3 metrics is that they are easily accessible with today’s wearables like smartwatches or other wristband devices.  If you don’t have one of these, I strongly suggest you purchase one.  I use an Apple Watch, but there are plenty of other wearables that get the job done.  Now let’s discuss the different ways you can estimate VO2 max or aerobic endurance using specific activities.

One important disclaimer before doing any of the tests below.  Be sure to discuss with your doctor to get clearance before doing these tests, especially if you have any significant risk factors for heart disease (high blood pressure, diabetes, history of heart disease, etc.).  It’s preferred you do this test with another person who can help with the measurements and also be present as a precaution in case you have any concerning symptoms.  If you are already someone who exercises regularly without issues, even when pushing yourself to higher intensity levels, this is probably less of a concern, but it helps to be safe and get clearance.

The Rockport 1-mile Walk Test

The Rockport 1-mile walking fitness test provides an estimate of your VO2 max.  The steps are as follows:

  1. Find a level 1-mile course. A high school track would be ideal.
  2. Warm up for 10-15 minutes of light stretching and walking to get the muscles warmed up.
  3. Start your stopwatch and walk as fast as you can for 1 mile
  4. After you finish, measure your time and also heart rate immediately after completion.  If you are just using a timer and not a heart rate monitor, then measure your pulse

You can input your information into a calculator like the one found here to estimate your VO2 max.  I like this test because it’s simple and easily accessible to individuals of all ages and fitness abilities.

The Cooper 12 minute Run Test

This test was developed by Dr.Ken Cooper in 1968 to measure fitness and estimate VO2 max in military personnel.  For this test you don’t need a heart rate monitor.  You simply run, walk, or run-walk as far as possible in a 12 minute period.  Your goal is to cover as much distance as possible in that 12 minutes.  Like the Rockport Test, it’s best to do this on a level track if possible.

This test can be done on a treadmill, but you need to raise the incline 1 degree to mimic outdoor running conditions.  If you can do either, I prefer your run or walk fast outdoors since that would mimic a more natural movement and setting.  See the chart link below where you would find the distance you walked in meter and match it up to your gender and age to see where you fall.

Cooper Test Chart

If you want to convert your Cooper test results to a VO2 max, use the calculator found here.


I have a Concept 2 rowing machine and was thrilled to discover that there is a VO2 max test available for this based on a 2,000m row.  Rowing is an incredible total body workout, so if you have a machine or access to a gym with a rowing machine, this is a great test to do.  I’m writing this during the Covid-19 pandemic and realize gym access is currently limited.  This test is simple because you set the row machine for 2,000m and row as hard as you can and measure your time to completion.  You can go to the Concept 2 site here to enter your time and estimate your VO2 max.

I call this the “Wolverine workout” since Hugh Jackman popularized it when he shared an impressive 2,000m row time of 7 minutes at the age of 48 which you can read about here.  My boys and I are big Hugh Jackman fans, so we love periodically doing this assessment.  It’s a brutal workout!

Improving VO2 Max

Now the key question is how do you improve aerobic fitness and VO2 max to live longer and better?  I would refer you to my exercise post here for guidance where I discuss aerobic exercise, anaerobic exercise and how to use heart rate during your workouts.  In an effort to not prolong this post any further, I can do a follow-up on this in the future.

The essential principle I tend to follow is the 80/20 or even 90/10 rule.  This means about 80-90% of my cardio workouts do not hit the anaerobic zone.  Remember, even if you don’t do VO2 max testing, you can use the Maffetone heart rate zone discussed earlier as a relatively good estimate.

Whether I’m running, hiking, cycling, etc., the majority of my aerobic workouts will be done at an intensity that pushes the limit as closely as possible without exceeding it so I maximize fat burning without hitting the red zone.  Now roughly once every 7-10 days I will do a more intense workout where I push my heart rate frequently into the anaerobic zone or I might sprinkle in very short duration sprints (15-20 seconds) during my aerobic workouts so my cumulative anaerobic workouts throughout the week don’t exceed 20%.

If I hit plateaus in my performance, if I’m getting sore and taking longer to recover, then I might take 2-3 months off to train exclusively in the aerobic zone with no anaerobic workouts at all.  This takes a lot of discipline and will power, but pays off in the long run.  By the way, the routine of doing mostly aerobic intensity and then sprinkling in some high intensity is called periodization which you can read about in more detail here.

Personalizing Progress

The tests I covered earlier are standardized tests that have been studied and provide age and gender-matched tables.  You can do your own personal test and assess progress over time.  For example, let’s say you have a favorite neighborhood 2 mile walk.  Measure how fast it takes you to do the 2 mile walk and then periodically monitor your progress.  If you are performing regular aerobic physical activity, your 2 mile neighborhood walk times should improve.  Some basic tips for different categories of individuals are below:

1. Beginning ExercisersMany of my patients have been mostly sedentary for decades and all of a sudden think they can train for a half marathon or do an intense bootcamp class even though they have no core, no flexibility, and very little leg strength and balance.  This is a recipe for grief and recurrent patterns of injury.

Work on your fitness foundation first and gently build up your aerobic fitness and then you can consider being more adventurous.  Read my part 2 exercise post here for some key exercise recommendations.  A good personal trainer or fitness coach will do a comprehensive evaluation first before subjecting you to high impact exercises and movements.  You might even consider seeing a physical therapist for more guidance.

Your aerobic heart rate zone will be very tight.  Because you haven’t exercised for so long, your heart rate meter will hit the red zone with even minimal exertion.  I strongly recommend you monitor your heart rate and spend at least 2-3 months building your aerobic base with 90-95% of your exercise sessions below the anaerobic red zone.  So if your limit is a heart rate of 140, stay as close to that without going above it.

2. Elderly Exercisers:  Same principles as above for beginners.  Start low and go slow and especially pay attention to your balance and leg strength since those deteriorate rapidly with age, and can really put you at risk unless you have been deliberately working on these areas.  Can you get out of a chair without using your arms? Can you stand on one leg for more than 20 seconds?  Given your age, the upper zone for heart rate will be lower.  For example, if you are 70 years old, you don’t need to exceed 110 (180-70) for most of your workouts.  If you are a lifelong exerciser, you might be able to push it a little more.

My in-laws do an evening golf course walk together and my father-in-law, who is highly motivated by metrics, noticed that initially during his walks up the steepest hill, his heart rate was 135.  After some time he noticed that his hill heart rate dropped to 107, a 28 point drop!  This means his heart is doing less work for a given amount of effort which is music to my ears.  It’s a sign that his cardiovascular fitness is improving and this is even more important to heart health than his cholesterol, blood pressure and other numbers which should still remain in check to minimize overall risk.

3. Intermediate Exercisers:  Once you’ve been at this for at least 4-6 months and you see steady progress in endurance and strength while maintaining flexibility, you can start diversifying your intensity by adding some HIIT (high intensity interval training) sessions and short sprints.  Now you might be ready to join a bootcamp or train for a race.  Listen to your own body, not your friends or your trainer when it comes to striving for these goals.  As you get fitter, your heart rate zone will also stretch a bit more so you can extend that upper limit by 5 beats or so.

You might consider getting a VO2 max test done, since some people find they can stay in the aerobic zone even if they increase their MAF heart rate by 10-15 beats per minute.  This is when exercise gets really fun since you can really go faster for longer while still burning mostly fat.  Do beware of getting hooked on the adrenaline effects of intense exercise.  There are times your body really needs to recover, so don’t backfire on your progress by piling on excess training days.

4. Youth:  More on children below, but thanks to their age, kids can exercise at a higher heart rate and do fine.  Dr.Maffetone has suggested an upper limit of 165 for teens below the age of 16.  They have a nice wide heart rate range and they also recover quicker.  The bad news is many young children and teens already look like miniature middle aged adults with a pot belly and lack of muscles and may be susceptible to injury if they haven’t been physically active.  Treat them a little bit more like the beginner case we discussed earlier to prevent injury, but they will progress more rapidly if they stay consistent.

What About Nutrition?

A big focus of my work over the years encompassed in my book, my blog, and my lectures has focused on food.  My patients who are averse to exercising try to solve all their problems through the diet.  My patients who refuse to change the way they eat try to exercise as hard and frequently as possible so they can eat whatever they want, whenever they want.  After treating and educating thousands of patients over the years I can tell you that neither extreme works.

You can build a bigger, stronger mitochondrial engine through exercise, but if you provide it with cheap, processed, dirty fuel, it will damage your engine and compromise your health.

Even if you eat clean, high quality foods, but eat them continuously throughout the day without adequate intervals of caloric rest, you cause mitochondrial congestion, leading to insulin resistance and chronic inflammation.  This is why practices like intermittent fasting and time restricted eating have become so popular and are so effective when done correctly.  They give your body, specifically your mitochondria in this case, time to repair and recover so by the time you are ready to eat in moderation again, they can efficiently turn nutrients into energy to help power your next exercise session.

I have seen and treated a large number of amateur, elite, and professional athletes who have had issues with diabetes, heart disease, and cancer.  They have spent a lifetime building and training their mitochondrial engines, but frequently fueled it with the wrong foods over the years and now are suffering the consequences of consuming unhealthy fuel sources.  Only after cleaning up their fuel source are they able to fully leverage the benefits of optimal health.

The good news is that today’s athletes are much more knowledgeable about proper nutrition, training, and recovery regimens so they not only compete at a higher level, but set a foundation for longevity and optimal health after they retire.  This is a goal we should all share.

Children and VO2 Max

This study published by the American Heart Association reports that 60% of American children lack healthy cardiorespiratory fitness (CRF).  I can tell you based on my own clinical experience and studies done worldwide, the numbers are even worse for certain ethnic groups like Asian Indians and East Asians where physical activity is increasingly underemphasized due to academic pressures.  I’m going to make a harsh statement here, so brace yourselves!

The sedentary lifestyle of today’s child is not the fault of technology.  It’s the fault of parents who fail to set priorities and choose brain fitness over physical fitness.

I have talked to coaches and PE teachers who say most kids nowadays can barely run a mile.  What used to be an effortless and enjoyable run for most kids is now considered an act of torture.  I even had a PE teacher tell me that he often gets notes from parents that literally say their child is incapable of running a mile and should be excused.

Staying physically active during childhood helps build the mitochondrial horsepower and energy needed to keep kids healthy now and later as adults.  Children with better aerobic fitness have an easier time stepping back into running or other aerobic activities later in life.  I have patients who were never regularly active as kids and simple acts like climbing stairs, walking uphill, or jogging take tremendous effort.  They take a long time to get into proper aerobic shape and are plagued with all types of injuries along the way.  They were never encouraged to build an aerobic foundation as kids because they were too busy building their resume from an early age.

Parents often overlook the incredibly beneficial impact aerobic fitness has on brain performance, memory, mood, and attention.

Physically fit children are not only healthier and happier, but perform better in school, just like fit adults are more creative, productive, and content inside and outside of work.

Take a look at the 2 scatter plot diagrams below from CureTogether from 23&Me, where they assessed which popular treatments were the most effective for depression (top diagram) and ADHD (bottom diagram).  This was based on self-report and the top right quadrant are the interventions that were the most popular and the most effective.  In both cases, exercise is in the far top right.  None of these other drugs, supplements, or lifestyle changes come even close.  In an ideal world, every single physician and mental health professional would prescribe a specific exercise program as a first line treatment for mood and behavior issues and then supplement with other modalities as needed.  That’s unfortunately not happening now.

Therapies for depression
Depression Treatments
ADHD therapies
ADHD Treatments

As parents, I would say over 90 percent of the verbal advice and feedback my wife and I give to our children is regarding self-care.  Teaching and encouraging them to eat better, move better, study in a healthy posture, manage stress better, get to bed earlier, and reminding them to get their exercise sessions in no matter how stressful academic pressures are.  Even our academic advice is focused more on time management rather than grades.

We encourage them to be more efficient with their time and to avoid overscheduling themselves so they have time to exercise more often, socialize with their friends, and just rest and recover with hobbies and non-academic pursuits.  I encourage all parents to consider doing the same.  Have them do one of the fitness tests and then monitor them every few months.  In school settings the 20m Shuttle Run test is the most popular test done worldwide.  In clinical settings with limited space, a standardized step test using a 12 inch bench is done.

As parents, you need to check on your children’s fitness test results with as much passion as you would their academic grades.

If your school does not offer fitness testing, hire a physical trainer or coach, send them to a physical therapy clinic or fitness center that does fit testing, and if they have any symptoms of excessive breathlessness, wheezing, etc., refer them to a medical clinic that offers exercise testing.  Just search “fitness testing” or “VO2 max testing” and see what you find locally.  My medical group, Palo Alto Medical Foundation, offers VO2 max testing for symptomatic children with a practice led by a highly trained pediatric pulmonologist, Dr.Mona Luke-Zeitoun, who is passionate about fitness in children.  She’s the one who shared the above images with me.

The general recommendation is for children and adolescents to get 60 minutes of physical exercise every single day.  I know many of you think this sounds impossible, but it’s a goal we need to help our children achieve.  Many of us may worry about our children not having a high paying, prestigious job some day, but we completely overlook the stress of being the parents of children who develop chronic physical and emotional health issues that could have been prevented if we had prioritized exercise and nutrition while they were young.

I know this firsthand because I take care of many multigenerational families where seniors worry 24/7 about their adult children (and even grandchildren) with chronic physical and emotional health issues that could have been partially or completely prevented with an emphasis on aerobic fitness and healthy eating during their childhood.  Your parents may not have had this knowledge, but you do now.  Don’t make the same mistakes with your own children.


We covered quite a bit in this post, so let’s summarize into some key takeaways below:

  • Optimal mitochondrial function is a direct indicator and predictor of optimal health and energy production
  • Aerobic function is a critical marker of mitochondrial function and disease risk.  Far more important in my opinion than any other single metric like glucose, blood pressure, cholesterol, etc.
  • You need to quantify your baseline aerobic status and then monitor it over time.  Options include VO2 max testing or fitness testing which combines measurable numbers like distance, time, and heart rate.
  • Prioritize physical fitness in children and track their aerobic performance.
  • You cannot live an optimal life through diet alone.  Fasting longer or lowering carbohydrate or caloric intake further can backfire and compromise health. Once you have nutrition dialed in, shift your focus to exercise, with an emphasis on improving your aerobic fitness.  Exercise is a far greater stimulus to upgrading your mitochondria than any food, supplement, or medication.

In our current sedentary environment, we are losing muscular and aerobic fitness at unprecedented rates.  It is essential that we track this and compensate for this deterioration by doing everything possible to increase our baseline activity levels while we work, by improving our muscle strength, and by performing regular sessions of aerobic exercise that enhance our mitochondrial function and overall health.


  • My blog post on aerobic training is here.  Be sure to read this if you haven’t already.
  • My podcast interview with legendary endurance trainer, Dr.Phil Maffetone (founder of the MAF heart rate formula) is here.  I strongly recommend you listen to this interview where we discuss all the nuances around aerobic exercise without increasing the risk of injury, chronic disease, and death.  A must listen!
  • For a comprehensive guide on VO2 max from Runner’s Blueprint, go here. They also have their own take on MAF here which I know is not for everyone.