I have a decent base level of fitness – I cycle 10 miles a day (commute by road) and do 10 – 30 miles on the MTB (off road in the Peaks) at a weekend (most of the time).
The first part of that sentence (I have a decent base level of fitness) appears, I'm afraid, somewhat contradicted by the second.
Base building is the traditional preserve of road riders. Ordinarily, this would mean long zone 1 and 2 rides. And I mean long – 100+ milers at least once a week. These days, people tend not to go for that level of base building.
For me, I try to build base in zones 3 and 4, on the road and on the turbo. The latter is just too tedious to do too much of the time, so i do 20 minutes of warm up/down and a main session of 90 minutes in zones 3 and 4. On the road, I'd do 3 or 4 hours of this, twice a weekend (with other riding in the week – currently mid-week tempo rides and riding a track SQT once a week).
I don't count commuting as the small amount of time spent on the bike and the stop start of my route means they're just junk miles for training purposes.
As time goes on, so you need to increase your physical and cardio strength for climbing, which usually means intervals. Do these at threshold. I've been using thesufferfest.com videos for a good interval thrashing.
Mainly, buy Joe Friel's book and get to it.
