Sacred Cow: VO2 testing ( also known as metabolic testing) is the best and most “ scientific” way to test/ascertain your fitness. By Sean Burke
My Take: VO2 testing is highly over rated and practically worthless for the most athletes.
I feel comfortable calling myself and expert on metabolic testing. I have a masters degree in exercise physiology, I’ve supervised hundreds of tests, and taught hundreds of undergraduate students to run VO2 tests on subjects. In the exercise physiology lab, we teach students to do these tests to help them get a better understand what is going on as exercise intensity changes. Researchers frequently test subjects so that they can classify the fitness level of the subjects, and then normalize the workload for each subject. When researchers run an athlete through the paces on a treadmill or a bicycle ergometer, the typically report the maximum intensity attained during the test. The participants then typically exercise at a certain percentage of the maximum intensity they achieved during the V02 max portion. This works pretty well for scientists. It’s a quick easy way to tell the general fitness level of the study participants, and how hard they exercised.
So why isn’t this useful for a bike racer? For many reasons. For starters, the information learned from the test is all based on the gases expired by the participant. The amount of oxygen a person uses, and the amount of CO2 a person produces tells us how hard they are exercising, and what they are using for fuel ( either mostly fat or mostly carbs). The volumes of these gases along with the respiration rate can also tell us what is frequently called the ventilator threshold. Now ventilator threshold is sometimes used interchangeably with lactate threshold, or even threshold power. These things are all highly correlated but they are not the same thing. Ventilatory threshold is when breathing rate and CO2 production begin to rise rapidly. Lactate threshold actually has many definitions but it is essentially the point at which lactate levels in the blood begins to rise. And threshold power is the power output that can be held for an hour. Again, these points are all highly correlated, but they aren’t the same thing. So if someone does a V02 test, they can learn their ventilatory threshold. If they do a test where blood lactate is taken, then they can learn lactate threshold, and if they do a field test with a powermeter, they can test threshold power. Further complicating the entire issue is that both lactate threshold and ventilatory threshold have several different definitions, and the definition you choose can make a big difference. The other things that can make a a difference are your fed state ( the last time you ate) and your training state ( rested vs not) .
Most people want to do a VO2 test because they want to improve their performance, and the goal of most practitioners charging good money for these tests is to predict performance or set training zones. But what people often forget is that the best predictor of performance is performance itself. That’s why I’m a fan of field tests rather than lab test. If you want to set training zones, they should be done using threshold power or your heart rate at threshold power. The most accurate way to test your threshold power is to put on a power meter and time trial for an hour. This method is awfully grueling, it would probably wreck you for a few days, and it is going to be awfully tough to find a course where you can ride at TT pace nonstop for an hour safely. That’s why I frequently use a 20 minute test. 20 minutes is still tough, but 20 minute power is going to be an excellent predictor of 60 minute power. The maximum 60 minute power that a rider can attain is almost always exactly 95% of their 20 max minute power. This is because at 20 minutes, the effort is almost entirely aerobic. If you go even a little bit harder you’ll fatigue rapidly. Same goes for heart rate. The 20 minute max heart rate is going to be an excellent predictor of 60 minute heart rate. (not quite as good as a 60 minute test, but almost). Why don’t scientists do a field test like this? It simply isn’t practical, when it is all done in a lab, it is easier for them to precisely control all the conditions during the experimental portion
So never forget that they best predictor of performance is performance itself. Don’t waste your money on an expensive test. Go out and do a field test. Many know that I’m a big advocate of training with power, so if you don’t already have a powermeter put that money towards a used Powertap. You’ll find them on Ebay starting at a few hundred bucks!
Sean Burke is the Head Coach for Crank Cycling in San Diego