Gaits Of A Horse In A Nutshell
Every saddle gait falls somewhere on the gait spectrum. At one end of the spectrum is the totally lateral pace. When a horse paces, two same side legs (right hind, right front/left hind, left front) move in perfect synchrony. At the other end of the spectrum is the totally diagonal trot, whereby two diagonally opposed (right hind, left front/left hind, right front) sets of legs move in synchrony. Both of these two beat gaits have a moment of suspension when both sets of legs are in the air. It’s the concussion that occurs when the advancing set of legs hit the ground that causes these gaits to be rough and jarring.
Saddle gaits are often referred to as intermediate gaits because they fall somewhere on the spectrum between the trot and the pace (as does the walk).
If a horse performs a gait similar to a trot, but the fore foot lands an instant before the diagonally opposed hind foot, then the horse is performing a broken, or fox trot. The timing of this gait is (lh--lf-rh--rf). It’s the same sequence as the walk, but with different timing. (The ongoing rhythm is unique, so that one can to say “Hunk o’ meat and peck o’ potatoes” very quickly to the beat of a fox trot.) When viewing the fox trot it does appear that the horse is 'walking in front, trotting behind' simply because there is no suspension between the picking up/setting down of the fore legs, while there is suspension behind.
If the horse performs a gait similar to a pace, except that the hind foot lands an instant before the same side fore foot, then the horse is executing an amble or stepping pace. Here the timing is also uneven: (lh-lf--rh-rf).
When an animal moves each leg independently, and no two pairs of legs work closely together, then the timing is an even 1-2-3-4 (lh-lf-rh-rf), and the gait is either a walk, rack or running walk. We all know what a simple walk looks like. The primary difference between the rack and run walk is that the running walk horse employs a longer stride behind, so that the horse’s hind foot sets down several inches ahead of the track of the fore foot. This is called over stride. Such long strides require the horse to use its head and neck as a balancing fulcrum–which explains the deep head nod. (To understand this better, walk quickly with as much speed and length of stride as you possibly can. See how you have to balance yourself by ‘nodding’ the upper part of your body?) The appearance here is one of 'walking behind, trotting in front' because there is a moment of suspension between the setting down/picking up of the fore legs, but none behind.
With the rack’s shorter, faster stride, there is little or no head nod. When ridden extremely fast, many running walk horses (I’m referring only to natural horses) revert to the rack or fox trot because there’s simply not enough time for the horse to use its entire body in the manner required for a true run walk.
Different breed descriptions may use various terms for these gaits, but regardless of the designation, all saddle gaits fall somewhere in the trot to pace gait spectrum–unless the horse walks on its head! Of course, variation along this spectrum is possible. The timing may vary so that one horse’s amble is slightly more square or lateral than another. One may perform a fox trot so that it is nearly a rack. Two horses performing the same gait with similar timing may appear dissimilar because of unlike conformations. Conformation has a significant effect on the horse’s inherent way of going. A horse with a very long, diagonally oriented arm bone, or humerus, for example, will exhibit much more lift in front than one with a shorter, more horizontally oriented arm.