This is the plan I'm starting to use
20 mins warm up to include;
15 mins progressive warm up until struggling to hold conversation
Followed by 3 x 20 sec sprints followed by 2 mins recovery after
each, then;
3 mins effort at 95 – 100rpm
Intensity should be such that you shouldn’t be able to carry on much
beyond the 3 mins
10 mins warm down
Complete over 3/4 weeks by adding an additional 3 minute effort each
week, taking 5 mins recovery between efforts.
I should add though that I try to get out on the road or off road a reasonable amount and try to still get 100 miles or so in to mainatin a base level of fitness