Jllmom, congrats to you for your work at the gym. I would definitely suggest taking some spin classes. Assuming you have good instructors at your gym, they will put your through your paces. Spinning is a very effective and fun cardio workout. If you go regularly, you'll end up doing both speed and resistance work. Go easy with the high resistance stuff though, especially at first. It's really easy to put undo stress on your knees during spinning if you push too big of a gear. I went to a class the other day where the instructor was barely able to turn her pedals over. In my opinion, that's an invitation to injury. Just listen to your body. If it hurts (in a bad way), pull back.

My best advice is to get a heart rate monitor and use it regularly. You didn't necessarily indicate that you're working on cardio fitness, but in my opinion, it's the foundation upon which to build all other fitness, especially in cycling. I'd recommend spending most of your time on the bike for the next couple of months at around 60-75% of your "maximum heartrate" (you may have to do some further research on how best to determine your max HR). Assuming you do this consistently, you will develop a good aerobic base. From there, you can work on increasing the intensity and duration of your indoor cycling and, hopefully, start riding outside as well. It may not be as immediately awarding as a sweatfest, but it will pay off in spades.

Cycling does build leg strength, especially in your quads, but since it's not weight bearing, it's not as effective as, say, running. You will notice changes in your muscle tone and definition as you continue to ride, but if muscle toning is your primary goal, I would also recommend doing some weight/ resistance training for both your upper and lower body. Interestingly, cycling requires core strength but isn't great at building it so cyclists benefit from supplementing their workouts with resistance, balance and flexibility training. In addition to riding outside and spinning, I lift weights and do yoga twice a week and do a ton of squats, lunges and crunches. I'm sure I could even do more than that, but that's all I really have time for on regular basis.

Good luck. Several people on TE that are training gurus, so I'm sure you'll get some good advice here.

Kate