The conversation is kind of trivial but I think it is one worth having. All the theories about what limits a runner during competition point to oxygen debt. So I guess the good news is we can all work on getting faster without going into oxygen debt during a race.
But I am still really curious what exactly happens when we are forced to slow down.
Noakes has the central governor theory. The central nervous system is in touch with the heart. Before there is a dangerous lack of oxygen being supplied to the cardiac muscle the brain slows the skeletal muscles down. he believes this because the cardiac muscle does not have the ability to go anaerobic. If pushed to an anaerobic level there would be a lot of people having heart attacks in races.
Traditional thought was that lactic acid was formed as a byproduct of anaerobic respiration and if enough accumulated the skeletal muscles would experience fatigue. As simple as that.
We have found that there is a little bit more to this. In solution lactic acid turns to lactate and that hydrogen ion. The lactate buffers the acidity of the hydrogen ion and some of it is actually reshuffled through the mitochondria. Once again though it is believed that the excess "waste" products produced at a rate the body can not deal with during anaerobic respiration becomes the limiting factor. The hydrogen ions win, the blood turns acidic and the muscles can no longer operate efficiently.
What Noakes has said is that the central governor keeps us from ever going anaerobic. That point at which lactate starts to build rapidly in the blood which is often referred to as the lactate threshold happens simultaneously as a result of a high use of oxygen. It happens at the same time because it is at that point that the central governor starts to realize the lack of oxygen danger to the cardiac muscle.
So I'm not siding with any of these theories. I'm just curious what others think because a lot of the theories contradict each other.