Hilda Gurney presents this video on the walk rhythm with her 26 year old mare.  She begins by pointing out that in a good walk there is a triangle formed by the legs. They use cavaletti set on an arc to improve the walk. She has the rider demonstrate errors a rider can make to make the walk worse including preventing the horse from nodding their head and rushing the walk. By using alternate leg aids on a poor example of the walk they show how lateral the walk can become until it is almost a pace.