Watch: The absurd conditioning that makes Regian Eersel a world champion

Dutch-Surinamese kickboxer Regian Eersel is a world champion for a reason. He has an endless gas tank in fights and out-works his game opponents. He earned his nickname 'The Immortal' due to his unrelenting cardio.

On April 22, Eersel will seek to defend his title against tough and smart German-born kickboxer Arian Sadikovic. Their clash will serve as the main event for ONE 156.

In his last four championship wins, the titleholder was able to fight the full distance. In each one, he showed unstoppable cardio. Watch the video below to see Eersel's latest title defense, which he won after going the full five rounds against experienced Dagestani Islam Murtazaev.

Over the five-round war, Eersel was able to out-stike his opponent en route to a decision victory. Impressively, Regian Eersel did not rest on the stool in-between rounds.

With his mind-blowing cardio, Eersel controlled this championship fight with leg kicks and punching combinations. His opponent turned desperate in the last few minutes of this championship fight, seeking a knockout to stop 'The Immortal'.

Fans will see if Regian Eersel can continue his winning streak and keep hold of his gold at ONE 156 against the dangerous Arian Sadikovic.

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Regian Eersel wants to do better in next title fight

Despite his lengthy winning streak and impressive displays of unstoppable cardio, world champion kickboxer Regian Eersel is looking to do even better in his next bout.

After his previous title defense, he spoke to ONE Championship, admitting he wasn't pleased with his performance:

“I'm not pleased. It was not my best fight, I think it was one of my worst fights, but I'm glad I got a win. I'm going to look at my mistakes and what I can improve. And I think it's maybe my schedule before the fight. It was like too busy, I think. And that's why, you know, fighting is also mental. So, I think this was a mental fight for me also. I'm going to work on it.”

With that in mind, Eersel wants to perform even better this Friday at ONE 156. He recently told ONE Championship that he will be aiming for a knockout this time around:

“I still would like to reach that level of fighting where I can put on a legendary fight that people will talk about for years to come. We will end by knockout. I’m not one to say things that will happen in the future, but I will do it easy in the third round. It has been three or four years since [I beat someone by] knockout, so this time I want to win by KO."