Of course he knows how much punishment the human body can take--he's Robin, whatever else he may be, and Batman had spent a great deal of time making sure he knew his limits.

Tim whirls to face Jaime, a panicked look on his face. "Jaime," he says, sounding relieved to see him. "What the heck is going on?! Mia just went crazy--started shooting at me!"

And it's obvious that he's been injured--he's playing up the poor, hurt Robin card, holding his arm stiffly, and looking pained.