Take the following quote from Jack Daniels – Daniels' Running Formula (2014) as an example:
[...] E running is typically performed at about 59 to 74 percent of V̇O₂max [...]
Here, the author seems to recommend a workout that keeps a specific quantity in a certain range relative to an individual's V̇O₂max value. As far as I can tell, similar statements can also be found in many other running or fitness guides.
However, I don't quite understand what this quantity actually refers to. What should I try to keep between 59 and 74 percent of my V̇O₂max? For the sake of brevity, let's refer to this mysterious quantity as X in the following. At first, I thought that X was the instantaneous V̇O₂ during training, i.e., the weight-normalized volume rate of oxygen that is consumed during training expressed in ml/(min*kg). The following points made me skeptical, though:
- If the considered quantity, X, really was the momentary V̇O₂ value, then it should by definition not be possible to achieve an X beyond the V̇O₂max value (= beyond 100 percent), right? Nevertheless, such X values seem to be possible.
- In this figure, there is a V̇O₂max region that is mapped to heart rates between 90 and 100 percent of a person's maximum heart rate, which should be way beyond the aerobic region. Nevertheless, V̇O₂max is also referred to as aerobic fitness, which is a bit confusing and makes me think that there is significantly more to this value than it seems at first.
It would be great if someone could help me clean up this confusion. To be more specific:
- What exactly is the quantity (X) that is expressed relative to a person's V̇O₂max value?
- What does it mean to “attain 100 percent of your V̇O₂max” in practice?
- Why is V̇O₂max also referred to aerobic fitness if it is achieved at such high heart rates?