Derived from the Greek word "hippos" (horse), hippotherapy refers to treatment or therapy aided by a horse. As far as I can tell, it is a sound system that addresses the motor skills that some autistic children need to improve on. Riding improves balance and posture, increases core strength and endurance. I would also expect the bonding between horse and rider to improve the attention and social skills of the child. Horses used in hippotherapy must be well-trained and gentle creatures. I would imagine the interaction between horse and rider to be both a calming and uplifting experience, resulting in both short- and long-term gains for the child that cannot entirely be measurable.