Old school said ride a fixed gear in the winter. Is this still a valid training tool? Any gearing and training suggestions for riding a fixed? I'm thinking of hitting the hills after my winter strength work at the gym, to make the muscle gains better adapted to the bike. Any ideas? Is riding a fixed OK for base miles, I live in rolling hill country so the heart rate could go over the 140 that is my target to stay under so I have some concern with that. Thanks for any info.