There's no good answer, but - - -
I've seen a big bear climb straight up a tree faster than I could run on the level.
I've talked to people who chased small bears and taken their packs back. And people who yelled and chased them. Those were bears which were just wandering through campgrounds.
I think the best chance a person has with a mad bear is to play dead until the bear gets bored playing with you. I've always had a dog with me, and bears don't like dogs. They have always either avoided or run from the dog.