The purpose of the shoot was to determine whether a galloping horse ever lifts all four feet completely off the ground during the gait; at this speed, the human eye cannot break down the action.
That’s ridiculously interesting, but is it really comparable to a walking speed human? Sounds more like an issue with the human eye than older paintings in general
If you look at the middle right image and compare it to the painting it's not all that wrong. Note: horse on right it jumping, not simply running. @ 20 seconds: https://youtu.be/oLvAxzVeyLs
Note that until Muybridge did his first time-lapse photographs, pretty much every single painting of a horse in motion was grossly inaccurate.
Compare:
https://en.wikipedia.org/wiki/Sallie_Gardner_at_a_Gallop
to:
http://images.fineartamerica.com/images-medium-large/fox-hun...