Instructions
Make sure the horse is comfortable with the owner and/or anyone who will be riding the horse. If there is a bond between the horse and rider and it feels familiar and comfortable then there is less chance of problems with the horse pacing.
Ensure there is no degree of discomfort which may be causing the horse to pace instead of displaying a more steady gait. A poor-fitting tack, teeth problems or improper trimming could all cause relevant discomfort and should be remedied.
Shift your body weight to encourage a smoother gait and to slow the horse down as it paces. Combine this with a pull on the rein and the horse will halt; but for a half-halt -- where the horse slows down but continues to move forward slowly -- you should loosen your grip on the rein and ask the horse to move more actively forward by shifting your weight slightly forward once you feel the animal beginning to halt.
How to Stop a Pacing Horse
The beautiful elegance of a horse is something which, in part, is down to its looks, but its ease of movement is another enrapturing facet to its charm. A horse with complete control and a smooth gait is a joy to behold and that is why it can be something of a frustration when you have a horse which, for whatever reason, finds itself pacing in a more manic fashion. There are a few things you can do to try to remedy this style, which can be a sign of nervousness or discomfort, but know that some horses will simply have a different style of movement from others.