**Abstract**

Besides "natural" gaits of walk, trot, and canter, selected horse breeds engage in the so-called artificial gaits, including the fox trot, running walk, and rack. Though some studies have been undertaken of these artificial gaits, the datasets are incomplete, sample sizes are small, and no comprehensive overview has been written. After reviewing the literature and detailing what is known about these artificial horse gaits, the authors present data of their own. Linear, temporal, and footprint parameters or given regarding artificial gaits of twenty horses total from specialized breeds. In addition to finding decreasing stride duration, lateral advanced placement, and tripedal support as one moves from the walk to the running walk to the rack, as with previous studies, we also found decreasing ipsilateral/diagonal step time ratios and increasing ipsilateral swing phase overlaps. Visually, the walk, trot, fox trot, and slow rack leave trackways of ipsilateral pairs in parallel rows, the running walk and canter leave trackways of isolated prints with the running walk pattern more symmetrical, and the fast rack, stepping pace, and pace leave trackways with an undulating pattern formed by diagonal pairs of hooves with hooves often crossing over the center line yielding a negative interior straddle.

**Keywords:** horse, gait, artificial, running walk, rack

#### **1. Introduction**

A gait is describable in terms of a footfall sequence of the landing and the liftingoff of feet as well as in terms of speed and coordination of limbs. When surefootedness is needed on slipper substrates walking gaits are best. In a walk, and at increasing speeds in a flat walk and running walk, as well as in the more laterally coordinated rack, the footfall sequence is RH-RF-LH-LF, and one foot is on the ground at all times allowing for great stability. At medium speeds a trot often occurs in horses, as it does in the zebra, wherein diagonal leg pairs move together in a twobeat rhythm, LH-RF and RH- RF. Such a gait seems to dominate in horse species that moved onto the steppes and plains where a softer substrate occurred along with a need for efficient locomotion over longer migration distances and speed to outrun predators. There is a moment of suspension in the trot and the trot is an easy travel gait for the horse and very efficient when a spring mechanism is present in the animal as occurred in monodactyl horse species. Some horse breeds now, and likely also in the past, could perform a medium-speed laterally coordinated gait of the

pace. In a pace ipsilateral leg pairs move together in a two-beat rhythm, LH-LF and RH-RF. There is again a moment of suspension. The pace is also found in camels and seemingly has some advantages in travel over certain substrates, such as sandy ones, and variegated terrains, as well as biomechanical advantages. The canter and gallop have a different rhythm and are asymmetrical. The footfall sequence starts off with RH-LH-RF-LF for the so-called left lead and LH-RH-LF-RF for the right lead canter or gallop and have moments where all four limbs are off the ground. The canter is slower than a running transverse gallop and the hind feet move in unison whereas in a running gallop the legs move more one after the other. The transverse canter and gallop are useful when speed is of the essence. In the rotary gallop, an advantage in sudden jumps or turns in the field, or needs instant acceleration, the hind front diagonal is replaced by the hind front lateral.

Horses will select their gait according to the stability, balance, maneuverability, efficiency, and speed needed within the framework of their anatomical configuration. They will also adjust their gaits to suit the substrate. Though we can forget this today, horses were animals of prey to which sudden outbursts and fast runs and maneuverability were a matter of life and death. Horses also have various traveling gaits when the herd is migrating. They also display unique ways of locomotion during courting and herding, or chasing away another horse they want out of the way for feeding reasons or to protect a foal (Renders, pers. observations). This is why they have a well-developed cerebellum responsible for determining the most suitable gait given a situation. Through continual study we are able to learn more and more about these gaits of horses. Here, in particular, we wanted to study horse gaits in their most spontaneous state, that is to say the gaits they most readily turn to and make use if left to their own devices. Still study of horse gaits does often necessitate, as here, observations on horses raised by trainers and so these gaits are in part "taught" to the horse, yet horses have an ability to switch between various gaits for diverse purposes, or to adjust the synchronicity and symmetry of the gait when desired. In other words though there has been a lot of focus on ideal gaits displayable in a show ring horses may often spontaneously opt for less ideal gaits that reflect more how they behaved in the past and in the wild.
