An item about dog grooming in something called Medill Reports mentions, inter alia:
Canine myotherapy, or muscle therapy for dogs, has been around since for “as long as people have been petting their dogs,” said Sue Olmos, a certified myotherapist at Midstates Myotherapy and Sanchez’s former teacher. While massaging athlete dogs can date back to ancient Roman times, being certified in the discipline is fairly new.
Searching for a source for this, I find a related claim on another site:
Ancient Greek and Egyptian literature includes illustrations of massage being carried out on horses, dogs and cats.
I wonder what an ‘athlete dog’ dog would be in Roman times … whatever the case, don’t eat that Elmer …