So I've signed up for the Oktoberfest Triathlon - a sprint on 25 Sept in Longmont, Co, just north of Denver, as I'll be out there for business. It only dawned on me today that I train at sea level in Boston and 300-1500ft in SoNH.
I'll likely be in Denver 3-4 days before the race. Any advice on pre-race training/adaptation and the race plan?
With 3-4 days before the race, you should start to acclimate. There isn't any way of training to make your body adapt quicker to that kind of elevation change. Make sure you hydrate the week or so before you get out there and drink plenty of water while you are there.
Drink a lot of water. Altitude will dehydrate you. Otherwise, manage your expectations. 3-4 days isn't enough time to really acclimate so just realize you will be sucking air. You are most likely to notice on the swim and run. If you go out too hard on the swim you will quickly find yourself not getting enough air.
I just did a couple runs and a swim at 7500ft and it wasn't pretty....especially on the swim. Really focusing on expelling as much air as possible under water helped some with the swim.
Like said before...hydration, hydration, hydration and the sun can be brutal. Got burned on a 40min run at 7:30am with SPF30 and it was only in the 60s but clear as could be.
As others have said, hydration before the race. Coming from sea level there really isn't a lot you can do to prepare and you will notice the thinner air. Good news is that I believe Oktoberfest is a sprint...it will be over quickly!