When it comes to racing at altitude, many resources recommend that athletes with a limited budget and little time arrive as close to an event's start time as possible—usually the same day.
Other sources recommend arriving between 18 and 47 hours prior to the event, commenting that there is no difference in the hours within that timeframe. An article I wrote in 1999 included research that suggested arriving anywhere between one and three days prior to the event.
There are many studies that look at the results of acclimatizing to altitude over one- to three-week periods. Few studies examine aerobic performance after short-term exposure to altitude because most conclude you should arrive as early as possible. After my experience outlined in Part One, however, I was reminded of one particular study examining short-term exposure. I was able to find it a few days before my 2007 Leadville 100 mountain bike race.
The Research
The study revealed that aerobic performance decreased by 11.3 percent within one to three hours of arrival at altitude. After roughly 45 hours of acclimatization, half of that performance, or 5.7 percent, was recovered.
The prospect of gaining 5.7 percent performance in an event that takes nearly 12 hours to complete looked very appealing. That gain works out to be about 40 minutes. All I have to do is get to Leadville a little earlier than normal for some free speed. Sweet!
However, the research paper (referenced at the end of this column) had a sample size of only five men. Additionally, the aerobic performance they examined was 50 minutes long. This is very short compared to a 12-hour event.
The testing protocol measured three exercise performances on three occasions. There was a low altitude test (600 meters/1,968 feet), acute exposure to high altitude (one to three hours after exposure to 3,200 meters/10,499 feet) and day three exposure to high altitude (3,200 meters/10,499 feet). The tests were named LA, HA1 and HA3, respectively.
Each test included the 30-second Wingate anaerobic test, a five-minute time trial and a 50-minute time trial. Between HA1 and HA3, test subjects were transported back down to 2,800 meters (9,186 feet) where they spent two nights acclimatizing.
My Experiment
Looking at the impressive results of the research, I decided to do a test of my own. I arrived in Leadville, Colorado, (3,094 meters/10,152 feet) about 66 hours before race start. The past two years I arrived around 20 hours prior to race start.
My performance would be between the city of Leadville and up to 3,840 meters/12,600 feet. I rationalized that staying in the city of Leadville would be better than going to a lower city like Copper Mountain or Vail. I was aiming to make the acclimatization days similar to the study, where performance was tested at altitudes higher than the acclimatization nights.
Researchers looked at change in arterial oxygen saturation and concluded that nearly all of the performance decline from LA to HA1 can be explained by decreased oxygen saturation and heart rate responses. I had the means to measure heart rate responses, but not oxygen saturation.
My Results
The first morning in Leadville, after 20 hours at altitude, my resting heart rate was 55, a full ten beats higher than when at home in Loveland, Colorado (1,524 meters/5,000 feet). The second morning at Leadville, my resting heart rate was at 50, a 50 percent gain back. On the third morning, race morning, my resting heart rate was at 57. Although this was higher than the second day, I was pleased because my resting heart rate is typically seven to 10 beats higher than normal on a race morning.
The chart below is a comparison between my 2006 and 2007 races, with heart rate and other performance data I collected using a Polar heart rate monitor. All of the zone times shown are in minutes.
| Zone 1 | Zone 2 | Zone 3 | Zone 4 | Zone 5a | Zone 5b | Zone 5c | Max. | Avg. | Avg. | |
| 2006 | 215 | 334 | 115 | 47 | 6 | 2 | 0 | 167 | 135 | 9.1 |
| 2007 | 127 | 295 | 131 | 95 | 13 | 3 | 0 | 169 | 139 | 9.8 |
I had a solid race this year, dropping 48 minutes off my time from 2006. You'll notice I spent more time at higher heart-rate zones and was able to drive a higher average heart rate and average speed for the entire race.
Examining all of the variables affecting the outcome of an experiment is very complicated. Although my time improvement is very close to the 40 minutes I estimated in my pre-race scheming, I do not believe that spending extra hours at altitude accounted for my entire race success. While I felt that my overall training this year was stronger than in the past, other factors affected my race too; and that discussion can be found here.
Although the research paper I mentioned earlier showed a positive result for short-term acclimatization and aerobic performance, it's only one research paper with a small sample size.
Recommendations for Acclimatization
I believe the extra time at altitude helped me from several perspectives. First, I felt more relaxed going into the race because I had extra time in Leadville to get organized. Second, I simply felt better on race day than I did after only 20 hours of exposure. Finally, my resting heart rate and heart-rate performances on race day showed a positive response.
If you have an important race at altitude, a few extra days at that elevation might give you a performance edge. Ultimately, you will need to see how your body responds. But for those that can afford it, the extra costs associated with time away from work and an extra night or two in a hotel might be worth it.
From now on, if I have a race that is important to me, I plan to arrive 45 to 66 hours prior to race start.