In my story, the main character is having a practice fight (in hand to hand combat). How could I describe this scene?

Here's an example for you: Leon and John circled each other, each one grinning at the tension they had caused in the room. Suddenly, Leon lept forward, charging his friend. Unprepared, John recoiled from a punch to his jaw with a wince. In retaliation, he prepared to strike his friend in the stomach, but he hesitated. "Don't do that," Leon told him before striking John in the shoulder with a hard fist. John fell backward with a loud thud. "It's fatal," Leon finished, offering a hand to help his friend up. "You could've done better."