All of that being said trying to run at altitude is hard. I did my first workout on a track Thursday at altitude, specifically 7200 feet. I ran 200s because one third of the track was iced over and I couldn't safely run farther. Anyway I was able to run the 200s within a second or two of what I would be running at sea level. That was not the problem though. when I jogged back to the starting line I would jog far slower than at sea level and never really get my breathing under control. In another example I was running a hard aerobic effort Tuesday in Denver on a treadmill. The pace I was running is one that is not terribly hard for me, except for running it at 5300 feet. As I ran the treadmill stopped at one point and asked to take my heart rate. I was thumping at 185. That is somewhat harder than what my heart should be beating at that pace. Yet both times my legs have not really gotten tired, I just can hardly breathe.
I know from limited reading that it takes three weeks for human bodies to start making more red blood cells, which in turn carry more oxygen, which in turn makes it possible to perform better at altitude. So two weeks into my new home at 7500 feet I still have not adjusted and am running nearly a minute per mile slower than normal for many of my runs. However, I remain hopeful that this physical stress will contribute to faster race times down the road.