Give out in the 4th? What a load of diaper fill.
Elevation isn't that taxing when the activity isn't taxing to begin with. In the Marines, we mostly trained at sea level in Hawaii, and prior to deployments our forced marches would get incrementally bigger. First little 5 mile admin hikes, building your way up to 10-15 mile full-load hikes, and then the clincher, the McCress 25 mile in 8 hour hump. The biggest live fire range in HI is on the big island between Mauna Kea and Mauna Loa at 6500 feet. We did all the prep hikes at sea level, but the McCress was always at 6500'. It was no more taxing than the others (except for the additional length).
I think the impact of altitude is only evident on the most strenuous activities. Pitching just doesn't fall in that category.