Joong Do Kwan's Taekwondo Applications

Joong Do Kwan's Taekwondo Applications
JDK Instructors share the passion with ITF friends in Perth

21 Dec 2007

The Knee is the Key ( Part 2)

In my last contribution to this blog, I looked at body mechanics during movement stressing how the knee needs to be bent to allow for the best, and most economical movement during training. Today, I'd like to address a common problem when attempting to keep one's knee bent, which I'd like to call "the moving wall syndrome".

A big issue that beginning students have with the knee is that, as they start, they bend it to achieve a good looking stance, but in transition as they move forwards, they straighten their legs, and then bend the knee once they've finished moving. Suddenly, their energy is directed in an up and down manner instead of forwards towards their opponent. You can tell that you are doing this as you move forwards because you will actually witness the wall across from you moving up and down. I can still remember my first Sensei walking calmly up to one of the dojo walls, placing his hands on it, and calling back at us "It's o.k. now.. I'm holding it steady for you." This was his humourous way of telling us that we are standing up, and going back down as we were moving in stance.

Not only does this up and down movement waste energy, direct power in the wrong way, cause more joint stress than necessary, but it also makes your body movement become more noticable to the eyes of your opponent. Why? Because your body is not staying in the same place coming forwards, instead it's visibly moving up, and down which activates the targeting system in the eyes. You only need to think about how difficult it is to track a ball that is coming straight at you, and to gauge it's distance in order to catch it, and compared that to catching a ball that is coming at you in a downwards arc.

"When an object of interest appears in the peripheral vision the eyes are rapidly turned towards it. The same ocular motor response may be provoked by a sudden noise or painful stimulus applied to the body’s surface. This sudden fast eye movement is called a saccade from the French word meaning the flick of a sail in the wind or the jerking of a horse’s head by a tug on the reins....... When a target is moving, the saccadic system can initially capture it but soon loses it as the image tends to slide off the fovea (termed retinal slip), necessitating another saccade. The smooth pursuit (SP) system overcomes this deficiency by enabling a target to be tracked smoothly rather than with a series of jerks, thereby keeping its image steadily centred on the fovea. To prevent blurring, movement of the retinal image has to be kept less than 5º/s. For the SP system to be effective, the target’s velocity has to be relatively slow, i.e. less than about 50º/s. If the target moves too fast for SP, the saccadic system is activated to recapture it. The latency period for a pursuit movement is usually 100–130 ms. ........Normally SP is triggered by movement of the target’s image off the fovea (retinal slip). During the latency period and from the retinal input, the brain first plots the direction of the target’s movement. The eyes then begin to turn in that direction and rotation accelerates to match the speed of the target. The accuracy of SP is reduced and its latency period prolonged when attention is distracted by a simultaneous second target.24 " To learn more about how your eyes target, and see movement click here.

Keeping the knees bent as one moves forwards: Whether in fighting stance, or in formal Traditional stance creates the least amount of body movement and contributes towards an illusion that you haven't moved as far as you have, nor as quickly as you have since the eyes have more difficulty registering horizontal movement. One minute the opponent is over there, and then almost like magic he/she is closed in. That's one kind of optical illusion that I would like to take advantage of when sparring!

2 comments:

Colin Wee said...

Good post, Mir.

I think you posted on a related subject regarding deep stances, C-step type walking, and kyokushin direct stepping.

The deep traditional stance does require lots of knee action. This is as opposed to the more upright way of walking which requires less knee action because you don't require to move the centre of gravity so far forward or to 'cross over' the hump and drag the back leg through.

I reckon that this is done because the traditional deep stance plus knee action is there to generate lots of power for a finishing blow - and end point during the encounter.

The shallower stances, direct stepping, and more upright stances are more appropriate for maneuverability, deflection, parrying, slipping, retreating, side stepping, etc. Meaning that in an area which allows you greater movement and when you're objective is to trade blows or measure your transactions, the shorter stances allow you quicker movement in all directions.

However, once you need to generate lots of killing force (life for a lunge punch), you'll need to engage much more knee action to drop the COG and surge forward. This is not necessary in sparring and can in fact be totally omitted during most light sparring matches.

The knee however is mostly forgotten in modern day practice sessions. Even in kicks, many practitioners may lock out the supporting knee and then fire kicks off at mid to upper level targets. Locking the knee out prevents control of body dynamics. Without such control, power transmission from the ground up is done only at the hip - which reduces the power generated, not to mention increases the probability of joint injury to torque-ing forces. An analogy might be punching at an opponent with a frozen shoulder ... or with the arm that has the tennis elbow. Ha!

Good post.

Colin

Colin Wee said...

Tang Soo Do: Pyung Ahn Cho Dan