61: Yoo-Sin U-shaped punch, what's it for?

About a month ago, kickboxer Gabriel Varga caused a stir when he released his video five stupid things karate teaches you. One of these was the idea of punching with both fists at once, using the mountain punch (yama tsuki in Japanese) as an example.

In taekwondo, this movement only ever appears in pattern Yoo-Sin, where it's called a "U-shaped punch". But it's in multiple karate kata, most notably Bassai Dai.

Varga is correct that it's mechanically weak to punch with both fists at once; you can't apply hip torque the way you can with a single punch. However, most karateka in the bunkai community do not interpret this movement as punching with both fists as once, despite that being the "standard" interpretation.

(Left) In Karate-Do Kyohan, Ginchin Funakoshi shows the movement applied against a hair grab, an idea General Choi copied in the Encycopedia of Taekwon-Do. (Right) In the Bubishi, a similar hair grab defense is employed, but as a simultaneous throat and groin grab rather than double punch.

The "double punch" idea has its defenders. Ramsey Dewey pointed out that in sport taekwondo he used it to set up a kick to the head, and online I've read it works well as a push. 

Other interpretations is that it's only one hand that's doing the punching. Iain Abernethy for example interprets it as an overhand punch while the lower fist is pushing down the opponent's arm.

Iain's interpretation
Source: PracticalKataBunkai

A slight variation of this is Noah Legel's interpretation of an overhand punch while trying to pin the opponent's other hand. Later in the video, he also applies the lower arm as a block.

Source: Peaceful Warrior Martial Arts

Alternately, it could be the upper arm that is blocking while you are doing an upset punch to the ribs. This actually looks like an old-time bare-knuckle boxing technique

They look similar

Blocking high while punching low, blocking low while punching high, both make a little more sense than punching with both arms at once.

Grappling Interpretations

The movement has also been interpreted as grabbing the opponent with both fists, which leads into a throw. You could interpret the two U-shaped punches, performed together, as a throw utilizing the footwork as a sweep.

Source: Imagin' Arts

Other throwing interpretations involve more footwork, such as turning, which we do not do in Yoo-Sin.

Following the Angle Punch

Since in Yoo-Sin we perform the first U-shape block after an angle punch, we can combine the two movements into an application. One way to apply the angle punch is as a hammerlock or chicken wing lock, as shown in the image below.

From here, if the opponent resists, grab the back of their shirt. Use the lower arm of the U-shaped punch to pull the opponent's back shirt to your left and down while you execute the high punch to their jaw.

Angle "punch" to U-shape punch application.

Hopefully this post has given you some application ideas for the U-shape punch, beyond the "punching with both fists at once" interpretation.

60: Hansu supported arc-hand strike to one-legged stance

Let's do another Kukkiwon form application.

Hansu is a short but interesting poomsae. In the first diagonal sequence, four puzzling movements are performed. The first is perhaps the easiest to understand. You may use it as a parry while attacking the side of the opponent's jaw (this is why you are at a 45-degree angle), turning the opponent's head.

 

Demonstration as a bouncer/doorman technique.
Source: MMA Kabashi

Performance of Hansu on right by TaekwonWoo

Next is the twin upset punch, which we use as a takedown. Grab the opponent's ears from behind after turning their head with the jaw strike. Leap forward and pull them down forcefully, throwing the opponent. 

Throw Fails

If the throw fails, the form gives you two options.

The first is if the throw fails but the opponent's head is lowered. We proceed with a simple downward punch to the top of their head. Because we always want to strike through our target, not at our target, we end up punching through where our palm is placed (the palm representing the location of the opponent's head). This has the apperance of being a "target block", but I believe it represents a downward punch.

 

The second option is if the opponent's head is not lowered. We wrap our arm around their head and get a chin lock as we step backwards into the diamond block, restraining the opponent. 

"Diamond block" application. Sources: Kinetic Dragon Kenpo (middle), Returning Wave Systems (right)

For the final move, we can use the one-legged stance as a knee strike to the opponent's coccyx while we pull their head back.