It starts off slow in the reblog window, then speeds up as it loads completely, so it looks like they’re galloping faster as they get up to speed. ^_^
The awesome thing here is that they’re not just cut and pasted; each of them has a completely different motion cycle! Apple Bloom has a longer stride than the others and bobs her head a lot more, and Scootaloo keeps her body at a stable center while she flails her legs a lot faster.
(Source: themechanicalfox, via okaynadine-null-deactivated2014)