The Maximal Testing Advantage
Think of it this way, if we wanted to measure a race car engine, we wouldn't have it in cruise control at 70 miles per hour. We would take it through all the gears and speeds to understand how it works, and how that should be translated to performance.
Sub-maximal testing, which takes you just above your anaerobic threshold can be found at some athletic clubs and personal training centers. Using equipment like Korr, Cosmed FitMate, iMett and NewLeaf, which are more suited for this king of testing, the person goes just above their anaerobic threshold, and the technician stops the test. The reason for stopping involves a number of factors: no insurance to go beyond this level, limitations of the equipment, lack of understanding on the data points above AT, and even the lack of a medical emergency plan should something go wrong. Also, remember many of these systems don't measure actual CO2 production, a key variable in determining a metabolic profile.
Sub-maximal testing tries to predict your maximal level from a sub-maximal effort. That is like trying to tell you the maximum speed of your car from what the engine is doing at a cruise control speed of 55 miles per hour. The problem here is the research clearly points to the fact that sub-maximal testing does not relate to your maximum abilities, so using this to predict training zones rather than actually measuring those zones simply does not work.
In addition, many people get a false AT as the test progresses, having the technician stop the test prematurely which many times is simply a breathing response to just increasing the workload. Add to this that your maximum heart rate can be + or - 40 bpm from your age predicted normal, and you can see predictions don't work. Even if AT is accurately detected, there are 4 zones above AT that require sophisticated measurement to determine your zone. If you are going to perform a sub-maximal test, then you might as well use rate of perceived exertion in exercise, which will probably be just as good, and save the testing fee!
If you want real results, then you have to go to maximum with medical-grade equipment with a technician who is used to taking people to maximum effort, and has the necessary training and insurance for this purpose. You are likely to find this at a hospital or a medical clinic, but not an athletic club or personal training studio. Testing should also have someone not only trained in testing, but has a wide range of interpretation skills as these metabolic points are not always easy to interpret. Also, the simpler systems do not allow the test technician to manipulate the points and therefore determine your actual metabolic needs.