I have been going to spinning classes for about a month now. I LOVE them. I am almost 63 years old and would never, ever have thought I could or would do this.
A friend, half my age, talked me into it, and she was right to do so. I've lowered my resting heart rate from 72 to 68 beats a minute already.
I use a heart monitor and try to stay at about 80% or more of energy expenditure. I have lost only 4 pounds but I can feel a big difference in the way my pants fit and can feel the beginnings of stronger core muscles. I expect the weight to come off more quickly as soon as my body gets over the shock
Keep it up and enjoy.
Tejas