Your arms are heavy, when you swing them around they affect you - even when they don't hit anything.
Put your arms out straight in front of you and swing them to the left, you will find your belly /waist/hips turn to the right.
Your body and your limbs act as if they are separate objects, pushing and pulling against each other when they move. When your body pushes your arms about, the weight of those arms causes the body to be moved in the opposite direction.
If your arm was heavier than your body, even punching air would knock you backwards.
This is something Mongrol must take into account when the time comes to lay down his guns and get up close and personal:
A visual analogy I often use is to imagine holding the end of a resistance band in my hand as I work. The other end of the (imaginary) band is anchored in the opposite direction to whatever movement I'm doing, so for punching forward the band is anchored to the wall behind me.
For an inward sonkal taerigi with my right hand the band is anchored to the wall on my right.
This band represents the force exerted on by body by my moving arm. Looking at the punch again I can see that my arm is pushing my body backwards (towards the anchor point behind me), with the sonkal strike I am being pulled to my right (again, towards the anchor point).
Because our arms are always much lighter than our bodies these forces don't typically unbalance us, but they do have some small effect, and since that effect always operates in the opposite direction of the main action, it is a detrimental effect. This effect is known as the reaction force.
It is easy, and largely automatic, to compensate for this reaction force; you just lean into the action a little.
But that is not enough, in martial arts we are always leaning, or otherwise moving our bodyweight, in the direction of the strike. We're doing that anyway, to make more effective strikes, if we want to truly negate the reaction force we'll have to add something else.
The something else is the other arm. If I punch with the right I'll "anti-punch" with the left, pulling it in as I push out the right.
The left is the Reaction Hand, and the same resistance-band visualisation can be applied to it.
Now when I punch forward with my right hand, my left Reaction Hand is pulling the (still imaginary) resistance band. Only now the band is anchored to the wall in front of me. The reaction hand is pulling me forward into the strike.
In the right inward sonkal taerigi example the reaction hand (pulled to the right shoulder as in Won Hyo) pulls me to the left as I strike in that direction.
Using this resistance band visualisation on all the traditional movements can be very enlightening. Many of the more odd looking movements (san makgi, for example) become simple examples of best mechanical practice.
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| Sonkal ap taerigi from Choong Moo, action and reaction balancing. |
The Caveat.
The caveat here is, of course, that using your non-striking hand to generate a little more power might not be a wise decision in actual practice, when it could be doing many other potentially more useful jobs, not least of which is protecting your head.
As far as General Choi was concerned the reaction hand is nearly always used as I have described here. But if that hand was actually holding something, an opponent's arm, collar or hair for example, when you pulled it, wouldn't that be a far more useful strike?
You would gain a huge increase in impact as you would have an actual anchor to pull against, accuracy would be improved and the target would have to deal with being both pulled and struck.
I am sure that the "empty" reaction hand is in fact the alternative or secondary use of the motion, and the "full", grabbing, reaction hand is the original application for most strikes. This is based on research into the roots of Taekwon-Do, which run back through Japanese Karate to Okinawan Karate.
That said, the Reaction Force is one of Taekwon-Do's technical cornerstones, it is everywhere in the traditional forms and understanding it in a practical manner is essential to the practice of this martial art.
