[notahacker]

Think it's more to do with hilly, wooded courses unfavourable to horses and a requirement that the horse's heart rate remain below a certain threshold when inspected by a vet in the middle and end of a course, whereas the leading humans are maxing out their efforts

I don't think the Mongol cavalry would lose races to humans over any distance of steppe

[AngryData]

To be fair you can run a horse to death in a race, a human however isn't likely to die from running a race even to their physical limits.

[neaden]

Yeah I think on say, a proper road the horse would win at any distance.

[8note]

the road adds some infrastructure - i think at that point the person should get a bike?

[shagie]

1990: For a few joyous years there was the Man v Horse v Bike competition in Mid-Wales - https://youtu.be/vFlglZUIKO8

[donkey_brains]

Well that’s just not fair. Even the fastest human on earth can’t be expected to keep up with a horse riding a bike.

[twosdai]

There's probably some upper limit to it, i am not sure a horse could live through the ultra marathon moab race in the western us.