Really @Freda we are talking about Horse Racing not the Pony Club.
The very act of training a race horse has to cause stress to elicit the physical and mental responses necessary to compete at a high level of performance.
That stress involves pain. That's a fact not shit.
A trainer has to manage injury prevention and those stresses that cause pain or injury.
But if you think that a horse racing at peak fitness doesn't experience any pain even momentarily then you are in dreamland. Post race techniques are all about managing that stress, the inflammation and the associated pain. It might be an ice bath, it might be a walk in the surf at the beach, it might be a dose of bicarbonate to manage the lactic acid build up.