I came across someone noting that an English term for the [training area of Sumo wrestlers](http://en.wikipedia.org/wiki/Heya_%28sumo%29) is "sumo stable", and that "stable" is usually a word used for horses. She found it a bit funny. I'm not sure whether she meant "funny" as in "haha", or "funny" as in "strange".

Wiktionary doesn't have any definitions of [stable](http://en.wiktionary.org/wiki/stable#Noun) other than a place for animals, or the horses from a stable.

Do English-speakers view sumo wrestlers as being like animals, or is there a meaning of "stable" that I'm unaware of?