One Winter, during one of my once-a-decade resolutions to get fit, I decided to cycle the equivalent distance of the 2012 Tour de France, on a Mountain Bike attached to a Turbo trainer set up in my Garage (no hills, so not exactly a direct simulation, granted :) ). I dubbed it, Le Tour de Farce.
I purchased a pair of lycra cycling shorts with a padded arse, and one of those trip computer things to attach to my handle bars and started slogging away with only Spotify to keep me Company. For the first few weeks I struggled, but it was amazing how quickly the legs and cardio got into shape and I went from struggling to get through 20 minutes, to reeling off an hour or so of reasonably high cadence (relatively), interspersed with some full on sprinting. For hard core enthusiasts, my 20 odd miles a day, 4 days a week, might be insignificant, but I was feeling the burn!
I never got to the end of my goal though. Mainly because, attached to a Turbo trainer, I had no benefit from suspension and bits of me started going, well, a bit numb.. Sometimes they'd stay numb for 5 minutes after I'd detached myself, all red faced, sweaty and feeling good about myself. I was concerned I might be damaging parts of myself...
Must get back into it, but not for prolonged periods..