When to start circle training

At what point can I start training circles? What are the basic strength requirements?

Thanks

Technically, I can have 4 and 5yo start training circles by just doing circle walks around the mushroom. Some may be able to do the easier versions of ag walks at that age such as feet on slider in pushup position pushing backwards and feet on slider dragging in straight arm plank.

Another drill I use is they simply put their feet on top of the mushroom and walk on their hands on the floor in a circle around the mushroom. When they can do this fairly well, I might let them use the bucket.

So basically, some ability to support themselves. Being able to do the front, rear and side planks is beneficial.

Another drill that can be used is while in support on PB, they circle their legs around an object like a small barrel.

I've never really heard of any basic strength requirements but in general the ability to support themselves is required.