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Bipeds

horse walk

Horse in a walk
Horses are perfectly suited to demonstrate four-legged gaits. In the walk, the footfalls are evenly spaced over a cycle, so there is a 25% difference in phase between successive footfalls. To work out the phase of any leg, follow the lines connecting it to the left hind leg and add all phases. For the right front, you will get 75+50=125%, which is the same as 25%. The walk is perfect for low speed and stability. The result is nice and stable. The resulting leg order is fairly universal for tetrapods.

Horse in a trot
With four legs, you can move them in pairs. There are three ways to so so, and this is one: if the left front moves with the right hind (and the right front with the left hind), the pairs are 'diagonal': the trot. Please notice that the legs are on the ground for a shorter part of the time than in the walk. This is a general trend: the faster you go, the less time the legs touch the ground. This trot is less stable than a walk, but the higher speed ensures stability by itself.

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Horse in a pace

The legs can also be paired on the left or right sides of the body: the left feet move together, and so do the right ones. This is the 'pace'. Normally it is something camels do and other long-legged animals do, because it may help prevent the legs knocking into one another. Horses can be made to do it. The pace is nice for intermediate speeds.

Horse in a bound
The third way of pairing legs is creating the pairs on the front or the back end of the animal. This is the bound. Rabbits use it, but horses never do. You can see why a bound is not very suitable for a horse. Rabbits can make it work because they can get their hind legs well forwards underneath their body. The horse would probably fall on its face (no animations were hurt during the making of this web site).

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Horse in a gallop
This is where it gets complex. In a gallop, there is no simple arrangement of legs in pairs. Instead, the phase diagram shows that the footfalls are distributed unevenly over the cycle. The legs are on the ground for very short periods. In effect, the animal has no legs on the ground for part of the cycle, technically known as a jump. There are at least two varieties of gallops, but only one is shown here. It is very fast.