For one thing, ask your guide. He'll likely have some stuff for regular loaning, and would certainly have specific advice for his area.
You're going up a few thousand feet; lotsa thousands if up in the mountains. So, forget elevators and take the steps. Got a stadium nearby? Stadiums have steps. First walk, then jog, then start straining a bit, toward a run.
You get in the high country, "There ain't any air in the air, up there!"
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