Mr. Torres let us know today on Chasingglory.com that a) 5,000ft above sea level in Boulder is much harder than 5,000ft above seal level at the equator and b) he's not a geologist and Mr. Carney agreed that he's not a geologist either. Regardless, awesome run finishing up Lefthand canyon!
The Equatorial Bulge places locations at the equator 1.5 miles/7,920 feet higher, from the center of the earth than locations in the Himalayas and 13 miles higher than the North and South Poles. (http://www.npr.org/templates/story/story.php?storyId=9428163) I'm not sure what the difference between Colorado and Equador would be.
Since it is decreased gravitational force at altitude that decreases partial pressure on oxygen molecules which in turn makes it more difficult for our body's to assimilate oxygen (not a decrease in the count of oxygen molecules), it is distance from the center of the earth, not from sea level, that causes the effects athletes seek when training at altitude.
This would mean 5,000ft above sea level in Boulder is MUCH easier than 5,000ft above sea level at the equator, which includes locations such as Equador, Peru, Columbia, Kenya, Ethiopia, Tanzania.
From Wikipedia:
Equatorial bulge is a planetological term which describes a bulge which a planet may have around its equator, distorting it into an oblate spheroid. The Earth has an equatorial bulge of 42.72 km (26.5 miles) due to its rotation. That is, its diameter measured across the equatorial plane (12756.28 km, 7,927 miles) is 42.72 km more than that measured between the poles (12713.56 km, 7,900 miles).
An often-cited result of Earth's equatorial bulge is that the highest point on Earth, measured from the center outwards, is the peak of Mount Chimborazo in Ecuador, rather than Mount Everest. But since the ocean, like the earth and the atmosphere, bulges, Chimborazo is not as high above sea level as Everest is.