Theoretical training concept.
 

Lets say someone set up a training center in the "mile high" Denver Colorado area,and built up legally many thoroughbred's red blood cell carrying capacity [like Olympic athletes have done]there.
Now these runners get shipped out to races at lower elevation tracks to compete,would they have an edge in certain spots?

temporarily

Is that good enough....

Watch the horses that ship out of Arapahoe after it meet concludes in August. Have hit some bombs when they ship to Columbus. The altitude works as an angle for a small window of time and after that they become regular horses again. Only time I ever hit a true 99-1 shot was off this angle.

How about Sunland Park? Remember Mind The Bird. El Paso is 5000ft+

I think there was a trainer that did that with 2 yr old into California a couple years ago, I know I read it somewhere.