He's pacing himself appropriately. If he has problems, they will be much easier to deal with because they will be small enough to nip in the bud.

[Green puts his hands in his pockets, giving Charizard a hard stare.]

Keep going, but don't use your flames. If he's slow enough to get hit by your tail, that's the only exception.

We're going again, Masaomi. I'm training you until you understand.