Fundamentally we will talk about going from fast big to slow small within one of the reining maneuver. However speed transitions apply to all disciplines creating this subject to be a broad subject.
* Fundamentally- being able to go from one pace to another. without any brace or resistance.
the horse during a speed transition should be channeling its body driving from behind channeling energy from diagonal
*IF your horse doesn't have these tools in place you must work on your approach to the transition.
* Reaction to the cue. What happens when you ask for the speed transition. Know that all horse react different. You should be able to react in a positive way as the rider to keep the cue and reaction consistent.