Looking at running the Denver marathon at 5280 elevation. With only a couple of days to get used to the elevation, what affect will a major change (over 4,000 feet) have on my performance? I am an over 40 guy capable of running 2:50 at lower elevation races. Could this be a dangerous run or just a slower marathon? (10 to 15 minutes slower?)
any input, thanks
Yes 10 to 15 minutes slower. Go out maybe 30 sec/mile slower than you think you can do at sea level and then pick it up. Easy on the uphills (lots of gradual long uphills in Denver, that are barely perceptible to the eye but you'll feel it), and then you can open it up some on the downhills. Avoid oxygen debt at all costs. Drink plenty of fluids and good luck.
It won't be dangerous in any real sense. You'll just be slower at a given effort level. That effort level may or may not "feel" harder -- some unacclimated people just see a slowdown, but others also perceive it as being more uncomfortable.
As for how much it will slow you down, I'd count on 15-20 seconds per mile, so in the neighborhood of 6-8 minutes. I've never raced a marathon up here, but my half marathon times are in the neighborhood of 10-12 seconds slower per mile at 5280 vs. sea level (FYI: I'm a little slower than you -- 2:55 or so). But keep in mind that (1) I'm acclimated and (2) the longer the race, the more the slowdown.
Check out the NCAA Altitude Adjustment table for Denver. You probably want to look at D3 women 10K conversions (because that is the closest you will get to your pace) for an idea how much you will slow down and it will probably be a little worse than that because of the increased distance. As a percentage, all are the same for a given location, so you can just apply the percentage too, but a little more for longer distance.
As a percentage, all are the same for a given location, so you can just apply the percentage too, but a little more for longer distance.
This isn't right (unless I'm misunderstanding). The longer
the race, the more the pace slows down on a percentage-wise basis. So, for example, you'll only lose 3-4 seconds in a 1500 (so 3-4 seconds per mile), but then 20-25 seconds in a 5k (so 6-8 seconds per mile), 60-70 seconds in a 10k (10-12 seconds per mile), 3 minutes in a HM (15 seconds per mile), and 8 minutes in a marathon (20 seconds per mile).
Runworks.com has a calculator that you can play with to confirm. I find it to be very accurate except for the marathon. Last year I ran a 10 mile race at altitude about six weeks after running a HM at sea level, and it predicted my time within 5 seconds.
My post was not as clear as intended. For a given distance, the percentage is the same, ie. the 10K D1 Men is the same percentage as 10k D3 Women. But you are correct that the 5k would have a smaller percentage. Since the table only goes to 10K and refers to track racing, an additional percentage needs to be added to account for extra distance and for being on roads.