Use the Bassett non-acclimatized column if you have not been training at altitude for over 2 weeks. A rough rule is to subtract 10% of your power at sea level for every 5000′ you go up. Also note that the gains from acclimatization are not huge. We used this on RAAM to keep from going into the red through the Rockies. Over Wolf Creek Pass (10,800′) my power was down a bit over 20%, but it felt like my perceived exertion was just the same as it had been for the last 2 days. I was breathing pretty hard too, as some of you may have seen in the video.
Note the implication here: if you drop 5000′, you will gain power, assuming you are not a non-responder, according to the percentage gain for a non acclimatized person, but from your acclimatized level, due to extra red blood cells! This means you may be at 105% for a while. This effect will fade in a few months.
Aerodynamic drag goes down with altitude, so you may descend faster. Many records are set at 6000′ to 7000′ elevation because of this.
On acclimatization to altitude:
The take away from this is that unless you can spend a bare minimum of 2 weeks training at altitude, you are better off showing up just before the event and doing it. Roughly a third of the population are non-responders, meaning no amount of training at altitude will lead to any physiological adaptation. My brother is a non-responder, but I have never had a chance to find out if I am.
Also make sure you take care of yourself just like on all your other rides:
- Nutrition (~250cal/hour?), hydration (bottle/hour?), and electrolyte intake.
- Could you lighten your bike and gear and still be prepared for the event?
- Get some lower rolling resistance tires that will still be durable enough for the event? Here is the data: http://www.biketechreview.com/tires_old/images/AFM_tire_testing_rev9.pdf
- Keep your cadence up in the zone where you are most efficient. Don’t let it drop 30 revolutions just because you are climbing. Get more gears if you need them.
- Biggest predictor of climbing performance is power to weight ratio. Shed pounds or get better at producing aerobic power, whichever is easiest.
Hope this helps!