J.D.
I LOVE spinning. I started doing it after my son was born 5 years ago and I have continued to do it after my other two children were born in the last 4 years. It will make you want to die at first, but stick with it! I threw up the first time I took a class, no kidding!! But I made myself keep going. It seemed like a month went by and I didnt notice anything happen to my body, but all the sudden after that pounds starting melting off! I went from 150 pounds to 121 in 4 months! I added 30 minutes of weight training twice a week and a 4 mile jog twice a week. But I didnt add that until later, after I really got in shape. I will give you some advise that really helped me... i invested in a good pair of spinning shoes. YOu can get them at bicycle or sports shops. They really helped me become more efficient when I spun, plus it didnt make my feet hurt as much like they did using the tennis shoes.
I stay stick with it! I have a friend that even continued spinning up until her ninth month of pregnancy. She was in such great shape!! Good luck!