Tai Chi as a martial art has both fighting applications and health benefits. Dr. Paul Lam of Sydney, Australia has put together a nice series of DVDs teaching the benefits of Tai Chi for the elderly and infirmed. His introductory DVD Try Tai Chi is a 45 minute sampler of moves that benefit patients with arthritis, diabetes and other similar diseases. His five part form stresses fluidity of motion and slow pacing that should help patients get exercise without taxing their bodies too much.
With any essentially unsupervised exercise there is the possibility of something going wrong and Lam's program is not a direct substitute for an actual Tai Chi class where the instructor can give direct feedback to students and make sure that nothing is done in a way that could cause damage. But Lam is a good enough instructor that, if followed closely, his mild movements shouldn't be a problem.
The program spends a good deal of time teaching warm up and cool down movements to make sure that even the most inexperienced student is ready to begin and finish. These exercises are performed by a group of mostly older students, showing that these slow movements should be possible for just about anyone. The five movement set itself (which consists of moves designed by Lam to work together and give a basic Tai Chi experience) follows these exercises and is taught piece-by-piece by Lam together with a student. Lam's instruction is pretty clear and his own examples are impressively fluid and natural. As always, the names of the moves can get pretty fun, with the best one here being "Fair Lady Working at the Shuttle."
Lam follows the entire program by demonstrating the set himself, first shot from the front, then from the back, to give the student the chance to see the movements from multiple angles. A really slick presentation of this material would have utilized DVD's capability for multiple simultaneous angles, but I guess that's not really necessary. Regardless, this is a good program for older folks to get their first taste of Tai Chi.