In that case, age-appropriate isn't the thing, it's getting too intense, and too rough. Because I don't care how old a kid is, they can still hurt someone if they're not careful. Ask any dad who has ever had a kid just the right height run straight at them.

Humans are a lot like puppies in this arena - we learn how to play without hurting each other by playing rough with each other, saying "Ow!", stopping the game, and resuming. Does he have anyone in the house to play rough with? And if so, are appropriate boundaries being established?

Rough play is actually quite beneficial, when done right: https://www.psychologytoday.com/blog/growing-friendships/201506/do-boys-need-rough-and-tumble-play

Other than that, I'd say he needs someone to step in and inform him when his play is getting too intense, as in the teeter totter scenario. He needs someone to point out how it can lead to injury. Little kids are pretty impulsive generally, and don't always think those things through.