Originally Posted by
Looigi
I'm in the ride-your-bike school and do hill repeats. I set up a ride with ~3 good hills and then do each one 3 times, killing myself toward the top each time. For longer hills, strength is never an issue if you have proper gearing for the max grade on the ride. It's all about aerobic capacity and muscular endurance.
This is my recommended approach to improving climbing ability also, and I don't think neglecting to do this can be made up for in the gym or with any other exercise. However, if the OP is looking to supplement hill repeats with gym work and running drills, I'd suggest doing stair climbing, because yes, climbing is about aerobic capacity, endurance.