I live near Philadelphia and am heading on a business trip to the Denver area. I've been running between 6-9 miles per week for the past 5 months. I'm wondering what I should be expecting to be able to run when I'm in the hire elevation. Should I plan on doing the same distances, or will it be less. I'll be up in that elevation for 6 days. Typically I do 2 days of 2 miles and a third day of 3 miles. Sometimes, especially as I get closer to our 5k races, I'll bump up to 3.1 all 3 days. Any help you can provide would be great.
I live at relatively low altitude - Los Angeles - but have traveled to Denver and other cities at comparable altitude (e. g. Albuquerque) a number of times. When running, you will need to breathe noticeably harder, compared to sea level, for the same running speed, and you will max out at a slower speed than at sea level. As Len noted, because the air is thinner, you're getting less oxygen with each breath. My experience is that I'm about 30 sec/mile slower in Denver than in Los Angeles, at least for the first few days. I have not needed to reduce distance (typical runs between about 4 and 8 miles).
@ 5K: Ontario Mills Run, Ontario, CA, 25:19
@ 10K: LA Chinatown Firecracker Run, Los Angeles, CA, 51:44