If you go to a profesional bike shop, you will find tandem bikes and you can get "trainers" which are certified for use with tandem bikes. These are devices that prevent the bike from going anywhere while you pedal. They suspend the bike slightly off the ground. Bikers use these to train or to "ride" during inclement weather. Just search for bike trainers and you'll get a feel for what they are. Our duaghter is a "biker" and uses a trainer in the winter. I checked and there are some for tandem bikes. Good luck!