Ah, looking around, I see that the technique is almost exactly the same as properly kicking down a door (just that you get more running leverage with a door). The leg-cock, the lean-in, the accelerated kick/push (rather than just a straight kick), it's similar to bringing down a secure door. See the end of this video:  https://www.youtube.com/watch?v=mVYX9-pMh4M  See this here, this is a perfect representation of using this technique: https://www.youtube.com/watch?v=cQ4OPBVGLVg Note that he's not just "kicking at door", it's more that he's got that running start (here, 15-30 cm of leverage), basically putting the foot on the door and kick-pushing it from a cocked knee in the air. He's not doing a karate-style/TKD kick, where you build up leverage from the foot on the ground, but rather from in the air.  Watch here, where a bunch of guys do basically martial arts kicks on the door, but then at 26 seconds the guy recovers, and simply kicks while extending his hips/getting that leverage, and pushing his foot through the door:  https://www.youtube.com/watch?v=EqQnDVqr7_g (unfortunately so many videos about "kicking down doors" are military, but still... You can do this At Any Size)