MichaelMc wrote:jamix wrote:"Lack of oxygen" is a limiting factor for Elites and non-Elites and even for "non-highly trained / non-Elites" runners alike! VO2max peaks relatively early in the progression of a developing athletes (and actually doesn't increase that much at all in some people). Personally I feel like I've hit that bar years ago.
That is a circular argument. You are assuming oxygen is the issue, and it isn't. VO2 max is NOT a good indicator of who will win a race, so it isn't "the limiting factor". Next, what VO2 max measures is how much oxygen you are able to USE, not how much you are able to get into your system. Availability is not the issue, hence oxygen is not the limit.
VO2max might not predict the actual winner in a field of elites with narrow pb ranges, but it's a great predictor of performances over a larger range and I imagine you'll almost never see a 20-min 5km runner having a VO2max higher than say a 15-min 5km runner.
As for the whole SUPPLY vs DEMAND debate, with regards to what limits VO2max, it has been found that oxygen supply is the limiting factor in most cases;
http://en.wikipedia.org/wiki/VO2_max#Fa ... ng_VO2_max
The factors affecting VO2 are often divided into supply and demand factors. Supply is the transport of oxygen from the lungs to the mitochondria (including lung diffusion, stroke volume, blood volume, and capillary density of the skeletal muscle) while demand is the rate at which the mitochondria can reduce oxygen in the process of oxidative phosphorylation. Of these, the supply factor is often considered to be the limiting one. However, it has also been argued that while trained subjects probably are supply limited, untrained subjects can indeed have a demand limitation
There can be Demand limitations too, but only in the untrained; And you certainly don't need to be an elite / highly trained athlete to become Supply limited.