Photo by Fan Zhen / China Daily

The culmination of these dozens of hours of punishing drills is a final totaling eight minutes in the ring. Each fight is two minutes, plus a minute or so for strutting and another 30 seconds between rounds.

Training started early summer. Fighters were selected halfway through. The 23 chosen contestants, including accountants, editors, researchers and engineers, joined the Brawl on the Wall event.

On the final night, Green is jumpy and energetic as he awaits his moment in the spotlight.

He seems nervous but insists he isn't. He says he knows he'll do well.

"I'm not going to die," he says.

"I know I've been practicing a lot. This is the reward - putting everything I've learned on the line."

The bell rings. The fight begins.

The crowd roars as punches fly.

Someone shouts: "Sam! Sam! Sam!"

The final bell rings. Green steps out of the ring.

He sees the world a little differently. That's not just because he's missing a contact lens and a shiner is emerging under his right eye. He lost the fight. But he still feels like a winner.

"Worth it! Totally worth it," he says.

"This is like the best experience ever."

Sun Xiaochen contributed to this article.