The Duel - a question

Just watched this great movie for the first time. I have a question about the duel between Candy and Theo. What was the purpose of the two other men standing to each side with swords out pointed towards the narrow dueling area? If one of the combatants attempted to step "out of bounds", were they to poke him back in?

You can see them towards the end of this clip with their swords out moving laterally mirroring the two duelists.

https://www.youtube.com/watch?v=A28ltTKn66g