The idea that fixed gear automatically improves your pedal stroke is a myth. A fixed gear actually encourages a lazy pedal stroke, as the gear carries your legs through the dead parts of the stroke. The only way a fixed gear improves a rider's pedaling action is by forcing him to pedal quickly. That's why "back in the day" road racers would spend the winter in a 65" gear. The folks riding around on a 49x15 are kidding themselves if they think it's improving their pedaling - a few months of riding around on a fixed gear at 80 RPM is often enough to throw a serious dead spot into the bottom of each pedal stroke, when the rider switches back to free.