jllmom - fair enough, if it is muscle definition and getting rid of fat that you are after, then riding your bike is the way to go. Much as most of us would love it to be true, spot reduction is impossible. Fat just comes off the whole body as a whole rather than in specific places I think. So I would concentrate on logging lots of hours on the bike which would help you burn lots of calories and really kick your metabolism into overdrive.

I don't know that riding indoors is harder physically by itself, but it sure is harder mentally. I tend to think the harder something is in your head, the harder it then becomes on your body. I'll do 2 hard workouts a week on the trainer and I always come away more mentally taxed than I would outdoors. Just think about it....no scenery, no wind in your face, no sensation of actually moving....you get the idea.

Unless the bikes you ride indoors (or your trainer), have large flywheels, the pedal action is different than it is on a regular bike outside. It has to do with inertia generally. On your road bike outside, you have much more momentum in keeping the pedals going....indoors, that's not nearly so well conserved.

Good luck