What is this stance shifting maneuver from Chun Kuk Do (maybe Tang Soo Do)?

Question

In the 1990s, I attended Virgil Davis Karate Studio in Flatwoods, KY. There was a form that one of the upper-belt students (I don't think he was a black belt yet at the time) did which had a section where he did a double knifehand block in a back stance, then did this odd shuffle where he shifted forward and kicked the thigh of his front leg with the sole of his back leg, then did the same, striking the back leg with the front leg. The impacts were sharp enough to create a slapping sound and took about a second total before returning to the back stance. For some reason, this has stuck with me in the years since I attended and I'm starting to wonder what exactly it was.

I don't remember the form name. I thought that it was one of the Pyung Ans, but none of them look familiar. At the time, the school was a Chuck Norris Tang Soo Do school, but partway through, it was rebranded as Chun Kuk Do, so the form might have come from either side. It could have also possibly been one from outside the style (at the upper belts, people often cross-trained, or brought in forms from styles they'd previously trained in).

What exactly is this movement? And what is its purpose? I've sent a query to my former instructor, but I don't know how often he replies to random emails.

Edit: After Steve Weigand provided some examples, I think there's a good chance this is Naihanchi 1, even though I don't remember that being part of the curriculum and the movement does not match what I remember exactly.

Answer 1

TL;DR - It is meant to represent a sweep of your opponent's leg or a kick behind his knees. With the prior techniques, you trap his arm and upper body, then you take him down with a sweep or a kick.

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Assuming you are indeed remembering Naihanchi Shodan, you are remembering a form that is likely around 200 years old, if not more. As with many modern forms of Karate, Tang Soo Do is largely composed of many small variations of ancient katas. This is not bad in and of itself, but it does mean that a few of the original bunkai are "lost in translation". In many styles, the Naihanchi series is formed of three katas that are taught when a student is nearing brown belt. This is because these katas mark the transition between a mostly "striking" karate to a mostly "grappling" karate.

Now I'm sure all would agree that karate is not a grappling art, but that's mostly because people tend to imagine stuff like wrestling, judo or BJJ when they think of grappling. A lot of Jujitsu and Aikido techniques solely aim at controlling the hands and the movements of your opponent without necessarily grabbing at their whole body and taking them down. This sort of hand-play is often called "tuidi-waza" (lit: seizing hand technique), or "trapping", in english. As the Naihanchi katas were taught in my school, they were mostly about learning tuidi-waza.

Let's have a look at the Tang Soo Do version of Naihanchi Shodan. The chosen technique comes towards the end of the sequence (Naihanchi Shodan is basically one sequence repeated twice). It is composed of the following movements :

1. A large sweeping right-handed Uchi Ude Uke
2. A left-handed punch
3. What seems to be a simultaneous Gedan Barai to the right and a second Uchi Ude Uke to the left
4. A left-handed striking Soto Ude Uke
5. And finally, that weird looking stepping motion, followed by a side strike

We did it a bit differently in our school, but the gist of it remains the same. Parts 1 to 4 show different ways of gaining control of your opponent's punching arm and upper body in a way that restricts his movements. Once that is achieved, that leg movement you see is meant to represent a sweep; by controlling your opponent's upper body and by removing one of his feet from the ground, you can unbalance him and throw him down. Depending on how you control your opponent's movement, you could also kick him behind the knees to achieve similar results. This is why the sequence ends with two of these sweeps, to indicate that the technique can be used with any leg and in different ways. Old karate katas are all about obfuscation of techniques, after all.

In this video, you can see an application of this technique. The prior hand techniques are somewhat different than what you are used to, but they serve the same functions. They are simply variations from one style/school to another.

In the past, I have also seen a few instructors interpret this technique as a defence against a kick/sweep. After your fight with the opponent in front of you, another opponent comes to the side with a kick/sweep to your leg. You dodge this technique and strike (weakly) to his head. While this seems like a plausible explanation, it feels "wrong" in the context of the Naihanchi series. The Naihanchi katas are usually very thorough in dealing with the imaginary opponents. Simply dodging one opponent before starting something completely different on the other side leaves that opponent free to attack you in the back (you merely punched him once). This movement is also the end of the main sequence, meaning that, at least traditionally, your opponent should be dealt with, not simply backing off from a single weak strike.

Answer 2

As a rule of thumb, anytime in a form you touch yourself, it is representative of touching your opponent.

The way you describe, I imagine the front leg crosses beyond the opponent, and thus begins your question: what is the back leg doing as it touches the front?

The answer could be one of several:

1) You are stomping on the inside knee of your opponent to off-balance them; the inference being that you don't have enough distance to kick to strike, but rather, to bend the knee to effect a sweep or off-balancing maneuver.

2) You are touching a pressure point area just above the knee to effect a painful response, mitigating their escape or counter with the inside knee.

3) You are wrapping your leg around your opponent, in order to effect prevention of escape or counter, or otherwise use his leg against you.

4) You are wrapping your leg around your opponent, in order to effect a throw; such a wrap makes it difficult for him to escape easily.

5) As an alternative movement (the Japanese refer to it as henka-waza) another explanation might be where you are avoiding a sweep, and you lift that leg to avoid it.

We see this movement occasionally in ITF but this seems more common in Karate styles. In ITF, we use this method from a horse-stance in Gae-Baek Hyung Yoo-Shin Hyung.

To study a movement, take note of what the hands are doing, what the previous movement was, what the next movement is, and where the eyeline is. These can all provide clues to deciphering what a movement does. You mention 2x knifehand block; that tells me you're not grabbing the opponent - rather, you're tending to push him back or keep him at bay.