I think it's good that I chose to go with just a regular upright bike, because that was enough. I found it quite uncomfortable after a while. If I can get comfortable with that bike then later I can work on getting comfortable on those "spin" bikes. When I rode my bike regularly I did get used to it and was able to go longer before it got uncomfortable, so I expect the same to happen here.
I managed the 30 minutes and actually built up a little sweat and a heart rate of 115. Not high, but for somebody 64 years old it's okay.
I limped off and went down the elevator and limped to the locker room. I decided to indulge myself a little by taking the disabled-persons' shower. I spent part of that time sitting on the seat in there and just washing the hot water over me. It felt good. Got dressed, went to the farmers' market in the parking lot, went home, still limping, still hurting. I think I will take some tylenol.