Once acclimated, you won't really notice it while cycling, though performance will be diminished overall. VO2 max is greatly effected by age and altitude.

Since I live at 9,000ft, am 64 years old, and often ride at over 11,000 ft, that combination has a big effect on performance. However, better riders than me up from the lowlands suffer a lot up here.

I do at times feel the altitude when Nordic skiing due to it's greater stress on the system. When I drop down to under 6,000ft while cycling in the Denver area, I feel like superman ... albeit an old one

Cheers, Tom

Loveland Pass at 12,000ft in early June


Snowshoeing at over 12,000ft last October ... A nice transitional workout between cycling and skiing seasons.


Uphill skiing (skating) at 10,000ft. This is the one that really sticks it to you ! Though technique plays a big part in this.