I'm sure that at one of Clare Rusbridge's first talks she said that the increased pressure caused by straining to pass a motion could cause extra pain.
I don't notice that Tommy spins any more than my fluffies, but he often has a session of mad face rubbing immediately after he has performed and none of the Chins do anything like that.
Cavaliers......Faith, The Ginger Tank and Woody.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.
Remembered with love......... Tommy Tuppence and Fonzi