After spending a week at altitude (around 8000 or 9000 feet), my body started to get acclimated to the reduced oxygen. Plus I got quite a bit of physical exercise with all the hiking. There was also the uphill sprint, where David, Ryan and I sprinted up a 60-degree rocky grade, cutting each other off and sliding for about 60 vertical feet. Man, we all panted when we stopped and could not catch our breath.
Anyway, I went for a run yesterday for 3.6 miles, plus a little walking to cool down brought me to 4 miles. I think that's my best run yet since probably track in high school! Go me! Or, go extra red blood cells! (Or is it an increase in 2,3-bisphosphoglycerate? I love clicking around Wikipedia.)