I wonder if a stair stepper would help in the same way. I have one that someone gave away in my laundry room in my building. It's like this one:

http://www.walmart.com/catalog/produ...de=cii_9324560

I hold on to the top of my secretary (furniture!) while I use it. I haven't used it much, but will do better. There's alot of resistance, and I think it may affect the same muscles as a bike.

This one is better because you can hold on:

http://cgi.ebay.com/New-Exercise-Wor...QQcmdZViewItem