KSI Collapses to the Floor After UFC Legend Demetrious Johnson Gives Taste of Leg Kick
UFC veteran Demetrious Johnson dropped popular YouTuber KSI with a single kick while training together.

KSI trains with Demetrious Johnson (via X)
UFC fighters frequently team up with social media influencers, producing entertaining content that draws millions of views from global fight fans. Demetrious Johnson recently traveled to the UK, joining forces with Michael ‘Venom’ Page and internet superstar KSI for training sessions. Their collaborative videos, showcasing playful sparring, quickly went viral and sparked excitement across both MMA and YouTube communities.
In the video, KSI asked Johnson to demonstrate how powerful a real MMA leg kick feels in action. At first, the MMA icon hesitated to deliver the kick. Eventually, he threw a kick, instantly dropping KSI, who couldn’t feel his leg afterward. KSI was completely shocked by how effortlessly Johnson generated such immense power with that barely-touched leg kick.
What the f** bro. Holy sh**. I have never been kicked before and he gave me what? A couple percent and I’m on the floor. It’s an instant dead leg. It just shut off my leg. It was crazy. He was literally just able to turn off my leg and I was unable to use it.
It is worth noting that KSI is a boxer who has trained seriously for years, evolving from a YouTuber into a committed and competitive athlete. He has participated in multiple boxing bouts, facing fellow influencers and professional fighters in front of millions of paying viewers worldwide.
‼️ KSI fell down instantly from just 1-2% of the power from Mighty Mouse’s leg kick 🦵😳
— IFN (@IfnBoxing) June 16, 2025
[Via – @MightyMouse’s YT] pic.twitter.com/tfSezmar7I
However, none of KSI’s boxing experience helped when Johnson ended things instantly with just a single effortless kick. Similarly, former World’s Strongest Man Eddie Hall once took a kick from UFC interim heavyweight champion Tom Aspinall during a training session. Even with pads on, Hall felt intense pain, proving MMA striking power is different from anything most athletes experience regularly.
KSI also got tapped out by Demetrious Johnson
Apart from the leg kick, KSI also tried to grapple with Demetrious Johnson in order to examine his ground skills. KSI wanted to survive at least a minute against the former top pound-for-pound UFC fighter. He started in the mount position to take advantage but immediately failed as Johnson managed to turn the tables.

In just seventeen seconds, Demetrious Johnson secured a dominant position and locked KSI in a submission, stunning the popular British YouTuber. Despite weighing only 140 pounds during filming, Johnson effortlessly controlled KSI, who weighed approximately 210 pounds at that time. Here are some reactions from fight fans after the video went viral on the internet:
KSI tried grappling with Demetrious Johnson and surviving for a minute, and only lasted 17 seconds 😭
— Championship Rounds (@ChampRDS) June 16, 2025
🎥 @MightyMousepic.twitter.com/GGtSUgIncy
BJJ is a whole different ball game man
— Ace (@AleksPetreski11) June 16, 2025
He let him start at the most advantageous position and still destroyed him.
— Only The Truth (@IMELTSN0WFLAKES) June 16, 2025
This is all of MMA twitter thinking they can survive or even beat dudes that actually train
— X (@fau1in) June 16, 2025
I wish they started on the feet, i wanna see how easily DJ could take him down and sub him
— Elonov 🇦🇺 (@ElonovMMA) June 16, 2025
DJ said how you want it
— Rocket🚀 (@TaemRocket) June 16, 2025
This wasn’t Johnson’s biggest opponent ever, yet he made the entire grappling exchange look shockingly easy and completely one-sided. In the past, the veteran has gone viral for submitting a 250 lbs opponent in a BJJ tournament. UFC veteran Joe Rogan also talked about that on his JRE podcast sharing how dangerous he is on the ground.