VO2 Max is a vital sign- why ignore it?

By: Dr. Gary Huber

Posted 10/31/2022

How “fit” are you?  What is my “fitness level”? This question is just as important as “what’s your blood pressure”?  Both can predict your longevity and your risk for degenerative disease. The category of degenerative disease is all the bad stuff that kills most Americans: heart attacks, strokes, cancer and Alzheimers.

The American Heart Association has stated that VO2 max, long used as a measure of running fitness, should be considered a “vital sign” by doctors.  So what the heck is VO2 Max? it is quite simply the volume of oxygen that you are capable of using in a given period of time. If I am more “fit” than Bob then this means I can take in and process more oxygen per minute than Bob can. I can exercise longer and harder than Bob which is a huge advantage in life. Analogy: a souped up muscle car with a big engine can go faster and use more gas (oxygen) than a Ford Fiesta. And . . . it’s more fun.

Low VO2 max strongly correlates with higher risk of a long list of serious conditions, including heart disease, cancer, dementia, Alzheimer’s, depression, and Type 2 diabetes. In fact, it’s a better predictor of longevity and risk of death than other predictors like smoking and high blood pressure.

Assessing VO2 max is key for those truly interested in understanding their true health status. If you are willing and wanting to explore what is possible desire a more exact measure of your current fitness level then let’s get to work.

As much as 50% of VO2 max from one person to another may be attributable to genetic factors  but this is also true for many or most of our physiologic measures. Some people are simply genetically predisposed for better VO2 max but this doesn’t change the fact that VO2 max is reflected by your lifestyle choices.  So, unless you trying to become a Tour De France champion the genetic difference matter very little.  Compare you to you. And like other measures of health this is “pliable”, it can change and improve with lifestyle changes so it is very dynamic.

Indirect Calorimetry testing engages exercise at maximum output with direct measurement of gases (O2 and CO2) inhaled and exhaled. This is the gold standard for measuring VO2 max, but even this rigor isn’t perfect.  There are other ways of estimating it. In descending order of reliability:

  1. Cooper’s 12 minute run (or bike) – maximal exertion x12 minutes and measure distance covered.
  2. METS measurement.  MET’s are “metabolic equivalents”. More on this later.
  3. Norwegian non-exercise estimate – simple estimate based on age, waist size, resting heart rate and exercise habits.

Where to start?  How do I estimate my VO2 max?

Method #1: General Estimate-
          "The Norwegian Approach"

Norwegian approach gets you in the ballpark but will never be as accurate as a true exercise test.

The equation used is:

  • Men: 100.27 - (0.296 x age) - (0.369 x WC) - (0.155 X RHR) + (0.226 x PA-index) 
  • Women: 74.74 - (0.247 X age) - (0.259 x WC) - (0.114 x RHR) + (0.198 x PA-index)

Notes: WC is waist circumference measured in cm not inches, RHR is resting heart rate, and PA is physical activity index which is a calculation shown below.

Example: 55 year old man, with a waist circumference of around 34 inches (86.3 cm), a resting heart rate of 62, and a physical activity index of 10. Plugging those numbers in gives you an  estimated VO2 max of 45.8 ml/kg/min. Is that good or bad? Discussed below.

Compare that to a 55 year old man, with a 38 inch waist, resting heart rate of 78, and physical activity score of 5: his calculated VO2 max is 37.6. He is getting dangerously close to falling off the cliff into rapidly declining health. He is inviting a cardiologist and an emergency room visit into his life. Completely avoidable.

This basic equations will likely underestimate many endurance athletes who truly train harder than this calculation is prepared to measure. But for the average Joe it's a good place to start until you can convince Joe to do a 12 minute run/bike.

PA Index:  physical activity index is arrived at by multiplying three numbers together,
Frequency x Intensity x Duration = PA

  • Frequency
    • 0 if you exercise less than once a week
    • 1 if you exercise once a week
    • 2 = twice or three times a week
    • 3 = exercise almost every day.
  • Intensity
    • 0 if you take it easy
    • 5 if you push to heavy breath and sweat
    • 10 if you push near exhaustion.
  • Duration:
    • 1 if you typically exercise for 30 minutes or less
    • 1.5 if you typically exercise for more than 30 minutes.

What if some of your workouts are longer and some are to exhaustion? Then fudge the numbers a bit to best approximate your habits. What if some of your intensity is to exhaustion such as TRUE H.I.I.T. workouts engaging Tabata or threshold time trials but others are shorted recovery workouts? Then maybe your intensity number would be a “7”.

When we look at longevity curves we see the greatest leap forward when someone goes from couch potato to modest exerciser. There are further gains to be seen as you elevate all the way up to “elite” athlete but these gains are smaller and smaller. This is not to say that it’s not worth pushing higher and harder but the people at greatest risk are obviously the couch potato and any movement is going to provide a large reward by comparison. Bottom line . . . move your ass.  Already moving? Great, move longer and harder.

Method #2: Copper's 12 minute Run

Coopers 12 minute run test to estimate VO2 Max: (my personal favorite). Ken Cooper is a brilliant physician, researcher, author, and military man who has decades of experience in the field of human performance and exercise. He formulated a simple field test that would approximate anyone’s VO2 max simply measuring the maximal distance you ran in 12 minutes. If you don’t run then fear not as we are formulating a “bike” conversion for those of you with bad knees, etc.

To calculate your estimated VO2 Max results (in ml/kg/min) use either of these formulas: 

  • Kilometers:   (22.351 x kilometers) - 11.288 = VO2 Max
  • Miles:   (35.97 x miles) - 11.29 = VO2 Max

Example: if I run 2 miles in 12 minutes (that's outstanding) then:

  • 35.97 x2 miles = 71.94 minus 11.29 = 60.6 ml/kg/min is my VO2 Max.

Copper offers this table as an example of age-related levels:

Method #3: MET's (Metabolic Equivalent)

A Metabolic Equivalent is a term used to compare one activity to another in reference to how much oxygen that activity requires. For example “1”  Metabolic equivalent (MET) is defined as the amount of oxygen consumed while sitting at rest and is equal to 3.5 ml O2 per kg body weight x min. One MET is approximately 3.5 milliliters of oxygen consumed per kilogram (kg) of body weight per minute.  So, we can use this to estimate VO2 Max. The exertion of walking up a flight of stairs would be 4 MET’s. Higher intensity activities hold higher MET estimates. If you are using a treadmill or stationary bike it may measure your MET’s for you and we can engage this as an fairly accurate measure of VO2 Max.

How to use MET’s:  after your warm up engage an increase level of exertion with the goal to get and hold your maximum output. How high can you hold that maximum output in a steady effort that lasts 1 minute? For example, if you can CONSISTENTLY hold an output of 14 MET’s for 1 full minute then multiply your MET’s by 3.5 to approximate your VO2 Max. If your max MET was held at 14 x1 minute then your VO2 Max is 49. If my maximum MET output for one minute is 15 then 15 x 3.5 = 52.5 as my VO2 max.

VO2 Max measure – Goals or Targets

The highest mortality risks are seen in those with VO2 max below about 18 ml/kg/min.

Once you get above 35 ml/kg/min, you’re in a zone associated with longer survival. The bare minimum functional level is roughly a VO2 max of 32. Below that, life just sucks.

  • Elite athletes – VO2 Max in the 60’s to 70’s.
  • Excellent is anything above 51
  • Good – 43 to 51
  • Fair – 34 to 42.    Whatever your current measure, simply improve it 5%.
  • Couch potato – VO2 Max below 32

If you have a low VO2 max, the only way to raise it is exercise. Higher intensity exercise that includes interval training is the best. Simply “walking” is great “activity” but it isn’t robust enough to be considered exercise. Put another way, no amount of walking is going to increase your VO2 max. You need to engage interval training at threshold levels to push VO2 max upward. I discuss starting points for interval training in the article High Intensity Intervals “Tabata” & “Peak 8” - tools for enhancing VO2 Max. I will be including more content on this topic and different options for interval training in an upcoming post. Having ways to estimate or measure VO2 Max in order to ensure that you will have the ability to function as you age.

 

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