At the Helsinki Olympics in 1952, Danish rider Liz Hartel became the first woman to ever win a medal in dressage. What was also historic about her achievement, though, was that her legs had been paralyzed since she was stricken with polio as a teenager.

Hartel had been an accomplished rider before she fell ill. However, instead of giving up the sport she loved, she continued riding her horse, Jubilee, as part of her rehabilitation. Then, as she stood on the podium and received her silver medal 51 years ago, she became living proof of the effectiveness of what soon came to be known as animal-assisted therapy (AAT).

For years, or even centuries before that, of course, what is now known as animal-assisted activity (AAA) has been enhancing the quality of people's lives -- from the lapdogs of Europe's gilded aristocracy, to the caged songbirds so beloved throughout Asia and beyond. This, however, was not medical "therapy," as it had no set goals. An equally long history can be claimed for AAT -- which involves professional therapists, animal trainers and veterinarians who create a special program for each patient. This dates back at least to ancient Greece, where the rehabilitation of wounded soldiers included a regular regime of horseback riding.