**4. Conclusion**

Horses are famous for their variety of gaits. For this, and for their amicable character, and indeed ability to interpret human facial expressions and bodily movements, they have become valuable companions and helpers of humans. They were domesticated for riding and pulling carts and now have a large presence in sporting events such as dressage, jumping, and racing.

Most intriguingly besides the standard diagonal gait of the trot horses are capable of various laterally coordinated gaits such as the running walk and rack which allow for smooth riding for humans and efficiency of locomotion for the horse as well as offering stability and balance depending upon the substrate. Here we wanted to further examine such laterally coordinated gaits and look at what is known about them and expand upon our knowledge of the gaits of these magnificent creatures.

In this investigation we found temporal and linear parameters that can be utilized to discriminate the different laterally coordinated gaits of horses. It is true that these gaits often occur on a spectrum, such as the rack, stepping pace, and pace. However, one can select criteria such as percentage of ipsilateral coordination and footprint patterns to distinguish the gaits. For example, the running walk and racking gaits tend to have an ipsilateral swing phase overlap of 50–75% whereas the stepping pace has an ipsilateral swing phase overlap above 75%, while, at the same time, the running walk lays down isolated footprints, the slow rack lays down footprints consisting of lateral pairs, and the fast rack and stepping pace lay down footprints consisting of diagonal pairs. Though we did not stress it here there are also behavioral and physiological factors that can be used such as amount of head nod or croup displacement or foot sprinting. Further study on these areas would be warranted, as would whether or not a medium-speed rack lays down isolated footprints that resemble those of a running walk and the biomechanical differences between the pulling running walk gait and pushing rack gait. Further study would also be quite beneficial on these asymmetries found in gaits such as the rack, as well as study of the spontaneous gaits of horses when lacking a rider which seem to often weave from side to side rather than occurring

in a straight line (perhaps to help avoid a predatorial attack). It would also be good to measure the angle each of the feet make in relation to the centerline in each of the gaits. Finally we were only able to record video at a maximum of 60 fps, and used 30 fps on occasion for the slower gaits (rather than the more common standard of 120 fps), which gives a potential error of 0.017 seconds, though this can be reduced in half by taking account of how close to making ground contact the hooves are in a given frame. Indeed someday when technology improves capturing video of animals in motion at 480 or even 960 fps would be ideal for a potential error of less than a thousandth of a second.
