I was told to do it to get off their kidneys but I now know that you don’t sit on the kidneys so I have my riders do it just to allow the horses to stretch out comfortably.
I make my lesson students keep the horses going at the walk or trot when they poop. “Keep him going Susie, he can walk and poop at the same time.”
Funny story, we were having a “practice show” at our barn and all the show riders and parents were there. My then 6 year old niece was riding the old 29 yer old lesson horse, Rozzi, who decided to stop to take a horsie fart, not a poop, just a raised tail fart.
“Emmy, keep Rozzi going, he can walk and toot at the same time.”
Emmy’s reply, “So can I.”
The parents still laugh about that one.