Horses suck at running

dailymail.co.uk

We have covered human running topics before (here, and here) , but this article provides a nice summary of how it all started: "persistence hunting".

Why nearly every sport except long-distance running is fundamentally absurd:

There's no denying it—our kind started substituting brains for brawn long ago, and it shows: We can't begin to compete with animals when it comes to the raw ingredients of athletic prowess...But there is one exception to our general paltriness: We're the right honorable kings and queens of the planet when it comes to long-distance running...
But then it finally happened—in 2004 a British man named Huw Lobb won [the Man vs. Horse distance race]...

Our long-striding legs are packed with springlike tendons, muscles, and ligaments that enable us to briefly store elastic energy as we come down on a foot and then recoil to help propel us forward. Tellingly, the most important of these springs, our big, strong Achilles tendons, aren’t found in early human precursors such as Australopithecus—it seems that the high-end tendons evolved along with other adaptations for distance running in the genus Homo when it appeared on the African savannah about 2 million years ago.
We’ve inherited large leg and foot joints from those ancestors, which spread out high forces that must be absorbed when running. To help ensure stability on two legs, we have big gluteus maximus muscles. (Chimps, which are incapable of distance running, have comparatively tiny butts.) Our clever torsos are designed to "counter-rotate" versus the hips as we run, also aiding stability. And we have an unusually large percentage of fatigue-resistant, slow-twitch muscle fibers, which make for endurance rather than speed...
But what most sets us apart as runners is that we’re really cool—we naked apes are champion sweaters and can dissipate body heat faster than any other large mammal. Our main rivals for the endurance-running crown fall into two groups: migratory ungulates, such as horses and wildebeest, and social carnivores, such as dogs and hyenas. They can easily out-sprint us by galloping. But none can gallop very far without overheating—they largely rely on panting to keep cool, and they can't pant when galloping, for panting involves taking very rapid, shallow breaths that would interfere with respiration when running. Dogs can gallop for only about 10 to 15 minutes before reverting to a trot, and so their distance-running speed tops out at about 3.8 meters per second. Horses' average distance-running speed is 5.8 meters per second—a canter. Wildebeests’ is 5.1 meters per second.
Elite human runners, however, can sustain speeds up to 6.5 meters per second. Even run-of-the-mill joggers typically do between 3.2 and 4.2 meters per second, which means they can outrun dogs at distances greater than two kilometers.
Our "sustainable distance" is also hard to beat. African hunting dogs typically travel an average of 10 kilometers a day. Wolves and hyenas tend to go about 14 and 19 kilometers, respectively. In repeated distance runs, horses can cover about 20 kilometers a day. Vast throngs of human runners, by comparison, routinely run 42.2-kilometer marathons in just a few hours, and each year tens of thousands of people complete ultra-marathons of 100 kilometers and longer.