The common saying in boxing is 'what happens in the gym, stays in the gym'.
It's a mantra that all boxers usually live by, and that's why they usually refuse to give too much information away about sparring sessions and training camps.
Every boxer will go through the sparring and the training camps ahead of big fights, and a Russian heavyweight by the name of Sergey Kuzmin is no different.
However, he's broken the boxing code and he's posted a video online of him knocking out his sparring partner, and it's safe to say this decision has not gone down well whatsoever.
Hundreds of fans have replied to the tweet slamming the heavyweight, accusing him of disrespecting the other boxer and telling him that he should have never posted the footage online.
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The knockout itself is brutal. Kuzmin lands a massive shot to the head of his partner, sending him crashing down to the mat. He then walks away to his corner whilst the other boxer lay flat on the canvas.
Kuzmin, 32, has a professional record of 15 wins, one loss and one draw in his 17 fights.
You can see the knockout for yourself in the video below.
Below is a screenshot of just some of the replies from the above tweet, and it's clear to see no one is impressed by the footage being shared online.
His CV isn't stacked with big names, but he has shared the ring with British heavyweight David Price, who he beat in the fourth round back in 2018, and he also went to battle with American Michael Hunter, who he lost to in September of last year.
Kuzmin isn't an elite heavyweight, and he won't be challenging for the main titles anytime soon, but he has managed to anger a lot of the boxing world with his decision to post a video of his sparring session online.
Yes the knockout is incredible, but remember, what happens in the gym, stays in the gym.News Now - Sport News