stairclimbing as a fitness activity

[LeeD]

Can't tell you, but it's the lateral collateral on the outside of the knee.
With my torn ankle tendons, I can go UP the stairs almost pre injury, but scarily hobble down even two steps. But I can't climb foreever, sooner or later it ends and I need to descend.

[tennisenthusiast]

UPDATE: Have been climbing 40 floors pretty religiously over past couple of weeks (2 to 3 times a week) and I haven't noticed any lower-back related problems.

I intend to keep this activity up.

1. What kind of muscles get worked out due to stair climbing?
2. What kind of changes (improvements) will I notice in terms of my play?