The first week I did two days commuting by bike, and took four days off.
Last week I cycled Wednesday to Friday, and was very pleased with myself for not having been on the tube for a week. But yesterday I was still pretty achy and complainy, so MCMLXX (Mrs MCMLXVII) suggested I leave it another day. Actually there's a lovely mathematical symmetry to that suggestion, in terms of building up my tolerance:
Week 1 - 2 days on, 4 off
Week 2 - 3 days on, 3 off
Week 3 - 4 days on, 2 off
Week 4 - 5 days on....?
Okay, so TOMORROW then. Yes. Just don't ask why my weeks have six days. Shh.