If you don't think stairs will help your cycling, try going to a gym which has step mills, those stairways to hell, and do an hour of mixed zones 2 and 3. If you can do that, don't worry about it. If you can't well . . . There are all those studies out there which say the fast folk hammer the downstroke . . . A local TT female does 30' of Z4, after warming up of course.

But yeah, of course I always take the stairs. If it's not many flights, I run them. My dentist is on the 4th floor and has outdooor stairs. I run them, twice a year, 2 at a time, just checking to see if I'm losing it. So far, so good, though of course I'm losing it anyway.