51: Choi-Yong supported backfist

Image source: TKDTube

Here I cover the supported backfist leap in Choi-Yong, as well as the high hooking kick (see an application for the middle hooking kick here). The explanation that the supporting hand adds power never satisfied me; the extra power is minimal. Instead, this technique can be applied as a wristlock.

One example is provided by David Gimerline in the gif below. The lock is a type of Z-lock, also called nikyo in Aikido.

Source: Kata for Self Defense Shotoryu Goshinjutsu

The backfist leap appears in other patterns and has other application. In Ul-Ji I prefer to think of it as a kotegaeshi (see the gif below). In Eui-Am it's likely pulling back the opponent's hair while pushing out their chin to throw them. It also appears in pattern Se-Jong.

Iain applying the opening of kata Bassai Dai (sampled in Ul-Ji and Se-Jong) as a kotegaeshi throw. Source: practicalkatabunkai

In the case of Choi-Yong, I prefer the Z-lock explanation, because it leads well into the next two steps in the form.

Another example of the Z-lock. By controlling the opponent's hand with your palm and putting pressure on the opponent's wrist-bone, they are forced to lower their head. Source: DetroitThreatManagementCenter

The form instructs us to perform a reverse hooking kick with the right leg. Turning around means we are getting behind our opponent. So one application is to simply perform a hooking kick to the back of the opponent's head.

"I can't kick that high" you might say. Okay: the very next step in the pattern is knifehand strike, which we also use to attack the back of the opponent's head. It's interesting that we land in a stomping motion after the kick. It may be that the intent of the kick is to hook and stomp into the opponent's right knee, forcing them down. 

Yet a third application is to swing your leg over the opponent's right arm while maintaining the lock, using your leg to lower their shoulder. I've seen videos of this technique before, but I'm unsure of the practicality.