VO2 Max - What is it and Why Does It Matter
The #1 Vital Sign For Longevity
Last week we discussed how an increase in activity and fitness meant a decreased risk of chronic disease including the leading cause of death, cardiovascular disease. Much of this can be contributed to changes in our VO2 max.
What is VO2 max?
VO2 is the maximal volume of oxygen that your body can take up and utilize during peak intensity exercise. When you exercise you breathe oxygen into your lungs where it diffuses across capillaries and eventually flows to the heart. Your heart then pumps this oxygen-rich blood to the body where it’s used by every tissue. During exercise, your muscle cells take up the majority of this oxygen to complete the work you are doing. The more strenuous the exercise, the more oxygen the muscles require to keep going.
If you've ever pushed yourself hard in a cardio session there is a point where your legs get heavy and your muscles start to burn. This is where your body no longer has enough oxygen to provide all of the energy it needs. The body resorts to using other sources for energy and the byproduct is lactate building up in your muscles. Eventually there is a point where you either:
A) Can’t get enough oxygen into the body and deliver it to the muscle tissues properly. This is called central fatigue. OR B) The muscles can’t utilize any more oxygen that has been delivered to them. This is called peripheral fatigue.
What Determines Your VO2 Max?
Peripheral fatigue is rarely the limitation on VO2 max so for today we’ll focus on central fatigue. These are the 3 most common causes.
1) Pulmonary diffusion - This is the ability to breathe oxygen into the lungs and get it to the heart. In a normal, healthy individual the lungs themselves are not a limiting factor of exercise. But somebody with COPD for example would be limited in their VO2 max by the ability to breathe in oxygen in the first place.
2) Cardiac output - This is the amount of blood your body can pump in one minute. It is measured as “Heart Rate x Stroke Volume.” Heart rate is obviously the number of beats per minute and stroke volume is the amount of blood your heart can pump with each of those beats. Changes in stroke volume (and cardiac output) account for the biggest difference in VO2 max between untrained and trained individuals.
A well-conditioned heart has larger chambers and beats stronger which means it both holds more blood and will squeeze out more blood to the body with each beat. This is because the heart has physically remodeled itself over time to become more efficient.
3) Blood volume and blood flow - Being well-conditioned means your body actually has more blood to pump. The body responds to consistent exercise by retaining more water and producing more plasma. This means a greater volume of blood and thinner blood. Thinner blood is easier to pump as there is less resistance in the blood vessels which means more blood (and oxygen) gets delivered to the muscles.
Why is it important?
I won’t beat a dead horse. To make this simple,VO2 max is about the best metric we have for longevity. The relationship between a higher VO2 and a lower mortality risk is clear as day. It can be considered another vital sign because of its significance. This holds true for both men and women.
Your VO2 max determines your ability to remain independent and whether or not you can continue participating in the activities that you love. For example, to walk 3 miles per hour would require a VO2 max of 12 mL/kg/min. And climbing flights of stairs consecutively would require a VO2 max of 32 mL/kg/min. If you want to be able to keep active with your kids or play rec basketball, the demands only go up from there.
If you lose your ability to maintain these levels, the activities you take for granted start to slip away. If we aren’t actively working to improve it, we will lose it. Most negative aspects of aging are really just a loss of physical fitness. While some decline is inevitable, much is due to lower levels of activity. On average, VO2 max peaks in your 20’s. For those training consistently it will peak in the 30’s. But when it comes to longevity, it’s less about the height of the peak and more about the ability to prevent the steep decline.
Every decade after your 20’s there is a 10% decline in VO2 max and a 15% decline every decade after 50. Much of this is due to a loss of lean body mass and an increase in body fat composition. Since VO2 max is measured in mL/kg/min, a higher body weight with lower muscle mass is a recipe for a lower VO2 max.
How is it measured?
The most accurate way to measure your VO2 max is in a lab with a graded exercise test. This is done with you hooked up to a machine that is measuring the oxygen you are taking in and the carbon dioxide you are breathing out. You go through a progressive increase every 1-2 minutes in speed or incline until you reach the stage where you can no longer continue. Throughout the test you get your fingers poked to assess the amount of lactate in your blood which indicates the intensity level at which you are training to validate the test.
Chris and I have both been on the receiving end of this test and have administered this test 100s of times in undergrad while studying exercise physiology. As you can imagine, it is not the most pleasant experience. Fortunately, it’s not necessary for the average person to do.
We discuss some at-home methods that can estimate your VO2 max here.
Take Home Points:
-Your VO2 max is the amount of oxygen your body can utilize during peak exercise. It’s an in-depth, snapshot of how efficiently your lungs, heart and muscles can all work together at a high level.
-It is highly correlated with longevity and if it’s not actively combatted, it will decline with age. Even if you are active, peak performance will still decline in your 40’s and beyond.
-The most accurate way to get a true VO2 max assessment is in a lab with a graded-exercise test but there are tests you can do at home.
-You can improve your VO2 max by up to 17% in one year with consistent exercise. That’s nearly 2 decades worth of capacity-loss restored with a more active lifestyle.
More on this to come.
Until then,
Brett
Brother2Brother
P.S. “What country’s capital is growing the fastest? … Ireland - every day it’s Dublin”