- Highest Points - The HC 1200 route reaches 10,000 ft. three times - at Cameron Pass (twice) and over the Snowy Range. By comparison, the Colorado 400k, 600k, and 1000k brevets reach 9,200 ft. The track record of riders from lower elevations (California coast, Texas, Maryland, etc.) on those events has been good. Most of these riders have reported more fatigue at elevation, but have otherwise performed well.
- Extended Altitude - One difference from the 400k/600k/1000k brevets is that more of the HC course is at altitude. The third overnight control, at Walden, is at 8,100 ft. (Saratoga and Steamboat Springs are lower.) Assuming you're reacting well to the altitude per se, you should still allow extra time for a slower pace and more rest. And stay hydrated.
- Acclimatization - True acclimitization takes weeks or even months. However, true acclimitization aside, some folks report they feel better after spending an extra couple of days at the start (5,300 ft.). There is also a theory in recent articles that it is better to arrive a couple days in advance, rather than a week in advance. Most non-local riders last year arrived 1-3 days in advance and most seemed to take the altitude well.
- Altitude Sickness - Data suggests that altitude sickness is very individual and hard to predict.* You're advised to do some research as to symptoms and treatment. While it may not be common across the population, you need be alert, know the signs of altitude sickness (a serious condition) and react to it quickly.
- Tips for Altitude - It's especially important to monitor your hydration at altitude. This is more of a challenge because the arid climate makes perspiration less obvious (and draws more water out of you). And of course mind the sunscreen, as the clear, dry (and somewhat thinner) air lets more radiation through.
Descending from 9,254 ft. on last Saturday's Lefthand Canyon 400km brevet:
* Some years ago, I came from Charlotte to ride a solo bike tour in Colorado, crossing a 12,000 ft. pass a couple days after I arrived and climbing to 14,000 (Mt. Evans) at the end of the trip. I experienced no altitude sickness, and am not an isolated case. However, as I said, it's hard to predict how a given individual will react.