What is the story of the "Five Animals Play" invented by Hua Tuo, the imperial doctor?

It is said that Hua Tuo went to Gongyishan to collect herbs when he was young. When he climbed halfway up the mountain, he found a cave. He is curious and wants to go in and have a look. Suddenly he heard someone talking about medical ethics inside, so he stood outside the hole and listened. He listened attentively, listened attentively, and heard the two men talking about Hua Tuo, which startled him. He was about to turn around and leave when he heard a man calling, "Since Mr. Hua is here, why don't you go in and have a chat?" Hua tuo had to bite the bullet and walk in. It turned out to be two immortals with white hair and beard. They taught Hua Tuo a set of fitness skills: imitating the postures of tigers, deer, bears, apes and cranes to exercise, which is the famous "Five Birds Play".