You use hand gestures to convey the idea of sparing in the danger room.
"What a novel idea." the champion says. "We will get you in shape in no time!" You and the champion squeeze into the danger room together.
You are pelted by wooden spikes but they mostly bounce off your armor. You don't take any injury beyond light bruising. You and the champion wrestle for over an hour bringing you to competant wrestler status. More impressively, you shoot up to professional armor user.
"Times up." A guard says. You and the other gladiators are led down a series of tunnels ending in a large copper wall and a weapon rack. The weapons on the rack are steel and of decent quality.