Re: Why moving too fast can cost you, especially at altitude
Posted: Tue Aug 31, 2010 2:48 pm
foweyman wrote:Ze's reference wrote: Well you should know that altitude has lower pressure and it's harder to get oxygen into the bloodstream and to the muscles. This means that if you are moving at a certain speed / workload, you are getting less of your energy from aerobic glycolysis, and more from anaerobic glycolysis!
I'm not doubting that there is an altitude effect, but it needs to be explained better. The above statement would be true only if the oxygen uptake rate was already at or near maximum, and couldn't be increased. It fails to account for the ability to increase the oxygen uptake rate by breathing faster and thus returning to the original aerobic/anaerobic ratio. Of course, breathing faster slightly increases the workload and oxygen needs, making it impossible to maintain the same hypothetical speed and workload as altitude increases.Ze's reference wrote:When you are hiking the last few miles up to the summit of Mt Whitney, you are already going slow as you can because of the low pressure
In addition to the missing word, this certainly isn't true. Although I'm sure others have been to the top of Whitney more than I have, I've never seen anybody move "as slow as they can" as they approach the summit.
You are right in theory, but in practice that's not the case...I guess I am speaking more of hiking without significant acclimation. People increase their ventilation/breathing but not enough to account for the decrease in pressure, probably because of hyperventilatory side effects they aren't used to. But after some length of acclimating, the adaptation would be better. That would be good to clarify.
As for the second quote, I'm exaggerating obviously. (And I'm too lazy too proofread, so thanks ). But it actually goes with your point; even though there is lower pressure ~14,000 ft, there's still plenty of oxygen pressure to do a lot of work, but people move slower when not acclimated and are avoided too much anaerobic metabolism.