Piaffe

originally used in battle to keep the horse focused, warm, and moving, ready to move forward into battle. The pony collects and trots in place or nearly in place. The center of gravity keeps the pony forward, ready to move. The pony calmly raises each foot with great impulsion without any suspension. The rhythm stays free and light as one foot always remains on the ground. There is a juxtaposition of great energy and control.

*taken from - The Human Pony: A Handbook for Owners, Trainers and Admirers found at http://www.greenerypress.com/