Posted by Dave on March 1, 2012 | 6 Comments
VO2 max, as we have discussed before, is a key measurement of endurance running ability. There are several different procedures for measuring it, and yesterday I got to experience one of the most common methods first hand.
As I mentioned last year, VO2 max is simply the maximum volume of oxygen your body can take in:
the key to muscle performance is delivery of oxygenated blood to the muscles, and adequate fuel to produce energy. Oxygenated blood comes from the lungs, and is pumped by the heart, which is itself a muscle requiring its own supply of oxygenated blood.
VO2 max can be seen as the maximum performance of this system: the amount of oxygen that can be effectively delivered to the body in a given time period.
As your workout gets harder and harder, you can’t continue to breathe harder and harder; there is a fixed amount beyond which your body can’t keep up. That fixed limit is your VO2 max. All that’s needed to find it out is a way to measure oxygen intake, and a way to systematically make a workout harder.
I have volunteered to participate in a study of the effectiveness of a dietary supplement on running conducted by Appalachian State University, which has a research lab near my home. As a baseline, they measure body composition and VO2 max of all participants.
Their protocol was simple: I got on a treadmill, put on a face mask that would measure my air intake, and started walking. Initially the task was easy: about 1.7 miles per hour on a 10% grade. But every three minutes, the workout was made more difficult by upping the speed and the pitch of the slope. After 9 minutes I was jogging up a 16% grade. After 12 minutes the task seemed difficult, but doable. I felt like I could keep this up for some time. Here I am sweating it out on the treadmill:
Then at 15 minutes the grade was increased to 20% and the speed was well over 5 miles per hour. Suddenly the task seemed nearly impossible. I kept it up for as long as I could — about a minute — but finally had to give up. This graph from my earlier article shows what was happening to my oxygen intake:
While this protocol was slightly different (with difficulty increased every 1 minute instead of 3), the end result is the same: At a certain point, I was unable to process more oxygen. My muscles weren’t getting enough oxygen to function, and so while I could continue for a while on reserve energy, inevitably I was forced to give up. The amount of oxygen I could process at this level of exertion is my VO2 max.
My VO2 max was 56.1, which is considered “athletic” for my age group. It certainly doesn’t compare to world-class athletes at their primes (Greta Waitz was tested at 73.5 and Greg LeMond was measured at 88).
If you don’t have a chance to participate in an experiment, you can estimate your VO2 max using one of many online calculators. How accurate is this method? I entered my recent 5K PR into the calculator and came up with a value of 52.9 — pretty close to my measured value.
There are some ways to improve VO2 max, but the consensus is that no one is going to make dramatic gains; there’s no way I’ll ever get my VO2 max up to a LeMondian 88. How much could I improve it?
One “easy” way to improve your VO2 max is to lose weight. As long as you’re only losing fat and not muscle mass, if you maintain fitness, your VO2 max should improve. This is because it is a measurement of oxygen volume per kilogram of body weight per minute. If you decrease body weight and everything else stays the same, VO2 max will increase. How much fat do I have to lose?
Fortunately at the same session I was also had my body composition assessed. To do that, the researchers had to measure my density. Since fat is less dense than other body tissues, they can then use a formula to determine the proportion of fat in my body. Since density is mass divided by volume, the key was to measure my body’s volume. In this past this was done by immersing in a water bath, but I got to try a newer method based on air displacement. I sat in an enclosed chamber while the air pressure was adjusted. Here I am inside the module:
I actually messed up the testing in a way the researchers had never seen: I sneezed. This changed the air pressure sufficiently that the sensitive device had to be recalibrated and I was retested. Finally the brutal truth of my body composition was revealed. I have about 31.9 pounds of fat in my body, compared to a total mass of 190.6 pounds. This means my body fat percentage is 16.7. Elite male endurance athletes typically have body fat of 5 to 8 percent.
In principle this means I could improve my VO2 max significantly just by losing fat. In reality less than 1 percent of active men my age have body fat levels under 6 percent. A more realistic goal might be to reduce my body fat to 11.4 percent, which would put me in the 95th percentile. But decreasing my body fat (and thus my total weight) by around 5 percent, would, everything else remaining equal, also increase my VO2 max by about the same amount, so in that way I should be able to increase my VO2 max to about 58.9. With training, I might be able to increase it another 10 percent or so, to the mid 60s. Still not world class, but not bad.