I love the spinning bikes at the gym. BIG steel flywheel fixed to the drive train so like a fixie the momentum pushes your spin. set the resistance anywhere in the spectrum. keep cranking it until you can barely move the pedals and try to maintain a smooth pedal rotation while you climb a monster hill, or back it off, and work on speed. My climbing and spinning both improved over the winter last year with spinning 2 or 3 times a week, and short commuting rides. Combined with rollers to work on balance and smoothness, and the winter could be a very productive time training-wise.