I was googling around for details of a Greek cavalry commander called Eumenes, who’s credited with introducing the use of pillars in training horses when I found this. As Xenophon put it, would you whip a dancer? Eumenes would.
During this siege, as he [Eumenes] perceived … that the horses would lose condition if they never used their limbs …. he caused their necks to be hoisted by pulleys fastened to the roofs of their stable, until their forefeet barely touched the ground. In this uneasy position they were excited by their grooms with blows and shouts until the struggle produced the effects of a hard ride, as they sprung about and stood almost erect on their hind legs until sweat poured off them, so that this exercise proved no bad training either for strength or speed.
From Plutarch’s Lives, sourced here.