Gravel Racing at Altitude

 I recently raced at Rebecca's Private Idaho, held on various gravel roads and trails around Ketchum, Idaho. During the race, we were consistently riding above 7,000 ft. elevation, and our high point was stage 2 of the race that topped out at 9,300 ft. on a hill called Dollarhide.

During that stage, I managed to finish 8th and should have been happy with that result, but I also had this nagging feeling that I ought to have done better because I only sustained about 90% of my FTP for a 25 minute effort [Strava segment].

That got me wondering about the effects of altitude on power output, and I came across this article from TrainingPeaks that gave me exactly what I was looking for:

In my case, the article would suggest I take my FTP of 335w, multiply by 105% and then multiply by somewhere between let's say 90.7% and 84.2% (the range between acclimatized at 7k ft. and unacclimated at 9k ft.). Acclimated is defined as several weeks at altitude. Non-acclimated is defined as 1 - 7 days at altitude. In my case, I had been at altitude for 5 days prior to Stage 2.

So, based on this table, my power ought to have been somewhere between 319w and 296w. Therefore, 300w for 25mins was within the expected range. Somewhat strangely though, my average heart rate was only 156bpm when my threshold heart rate is supposedly 168bpm. Maybe, indeed I had a bit more to give but I sure didn't feel like that, panting like crazy over the finish line :-)

By the way, the papers cited are as follows:

1. Bassett, D.R. Jr., C.R. Kyle, L. Passfield, J.P. Broker, and E.R. Burke. Comparing cycling world hour records, 1967-1996: modeling with empirical data. Medicine and Science in Sports and Exercise 31:1665-76, 1999.
2. Peronnet, F., G. Thibault, and D.L. Cousineau. A theoretical analysis of the effect of altitude on running performance. Journal of Applied Physiology 70(1):399-404, 1991.