Numbers are compact and easy to remember. A numbered list brings structure where none existed before. Being quantitative is the hallmark of a scientific method. Science is based on numbers. Hard data they call it, and that is true provided the numbers are meaningful. To be meaningful, the numbers have to be obtained through repeated and accurate measurements in carefully controlled conditions. The trouble is, none of the numbers I listed before were obtained in this manner. They are deceptive numbers used to hide qualitative assessments and personal opinions. They give you the impression of precision, accuracy and reproducibility where none exists. Meaningless numbers like that are as plentiful as weeds in an untended garden.
Some numbers are used to describe and compare fitness and training. Triathletes seem obsessed with such variables, but other athletes are taking notice as well. Often these individuals go to great lengths and spend serious amounts of money to have someone make a few measurements for them. It "helps" that health clubs and gyms see profits in making and interpreting such measurements. Unfortunately, the readings are often made in incorrect ways and more attention is paid to fitting a schedule and the availability of equipment than to what is actually being measured.
Not only are the data at best quite shaky, they are almost always used in incorrect ways. That is not necessarily the fault of the person performing the tests. These people are often quite dedicated and strive for accuracy. However, ignorance, tight testing schedules, and profit motives all conspire to derail good intentions. Quite often only a single value is obtained under sub-optimal conditions. No time for repeats, sorry folks!
Even more frequently that single value is then treated as a true reflection of reality without any consideration for variability and measurement error. The "true" value is then used in non-sensical comparisons to reach conclusions or draw inferences that are totally unwarranted and unsupported. Some will go as far as designing entire training regimens based on such questionable tests. These highly "customized" training regimens generally command high prices leading consumers to believe that they must be valuable.
Before you get too carried away, rest assured that there is nothing better than you best 10K time to assess your cardiovascular fitness. It is easy to measure, highly reproducible and you can do it anytime and almost anywhere. And in case you care, with the help of simple lookup tables you can get a very accurate estimate of your VO2 max and all the bragging rights that it entails.
All without spending a dime!