Originally Posted by
asgelle
There is absolutely no reason to believe this is true and good reason to believe it isn't. Taking the premise that the muscles weren't able to generate the required power primarily through aerobic metabolism, it doesn't follow that incomplete oxygenation of the blood was the reason. Other reasonable and more likely explanations would include insufficient stroke volume, inadequate difference between arterial and venous VO2, lack of intramuscular metabolic capacity, among others.
Yes my explanation was a little crude and I did lay a lot of the responsibility on the lungs for incomplete oxygenation when what I should have pointed to was general respiratory, circulatory and muscular efficiency. The problem, it seems to me was very likely was a shift to anaerobic metabolism.
Well let's see "insufficient stroke volume" suggests that the blood is fully oxygenated but that the heart can't pump it fast enough to supply the muscles. You are suggesting that the lungs are fully functional but the heart can't pump enough volume. Fair enough but the muscles are still not getting enough oxygen.
"Inadequate difference between arterial and venous VO2" is a result of the muscles not or not yet having removed enough oxygen from the blood supply. It results from not having enough slow twitch muscles with the needed capillaries to extract and process the oxygen.
"Lack of intramuscular metabolic capacity" would point to the slow twitch muscles having enough oxygen, fats and carbohydrates but not being able to process them. I assume you would suggest that this would be from not having enough of the slow twitch muscle fibers or that the ones our particular athlete has can't process all of the components fast enough. I have a little trouble with this one as the difference between 22.5 and 24.5 would not seem to matter that much to muscles having an adequate supply of fuel and oxygen. The fact that the OPs comfort returned fairly rapidly when he backed off marginally suggests to me that it would be a case of a problem with VO2max or Maximal Oxygen Capacity.
In short it seems to me that the OPs muscles were operating in oxygen deficit mode weather from inefficient lungs, heart or lack of capillary beds to supply the muscles. This whole collection of organs is designed to provide both fuel and oxygen to the muscles and it seems that the oxygen was in short supply.
Let me add that while I point to "inefficient lungs, heart or lack of capillary beds to supply the muscles", anyone who can keep up 22mph for a sustained period can't be that out of shape and I mean to cast no aspersions on Mr. BikeArkansas's fitness, merely the differential between him and the riders he was chasing.
I am open to hearing other explanations.