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Firstly I would like to say that all of the material contained within this blog is of my own opinion and any inaccuracies in technical content or other's personal quotations are completely my own.

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Thirdly, some articles have been published on my dojo website if you would like to read them in an easier format

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Thursday 16 June 2011

Iaido Training Session 61

Sweat, Tenouchi and Feedback

I find it slightly useful to have some engineering background knowledge as well as a working understanding of physics in the study of iaido. I'm not suggesting that one should spend every training minute pondering on the physical dynamics of a movement but it has it's benefits now and again. One of those engineering aspects that became a bit more obvious this evening was that of closed-loop control which I will explain later.

Anyway, this evening was a great session. With no sensei and a decision to not teach (too much, thanks to Harry who took over teaching responsibilities) I spent a good three hours just training. I started at about seven o'clock and spent the first hour or so working on Shohatto as planned. My main focus was on ensuring that the footwork was energetic enough and in balance with the cuts which I think is getting there slowly. I also experimented with a few kinds of feeling with the nukitsuke. I also tried something that Peter West explained to me concerning trying to get the body to go between the left and right hand while doing nukitsuke. This certainly has the effect of ensuring the left hand doesn't linger during sayabiki. The three feelings I tried were:
  1. To keep a certain amount of tension in the grip while doing nukitsuke so that the kissaki flew out the saya a bit during sayabanare. This does cause a bit of a jerking action though which is something I am trying to eliminate as it detracts from the final cutting action of the draw as well as sometime flicking the kissaki up above the cutting arc.
  2. To keep the right hand relaxed at sayabanare and slowly build up tension so that the kissaki smoothly reaches the correct angle and height.
  3. To reverse the tension of the right grip so that the mune of the sword pushes against the bottom of the saya until sayabanare is completely achieved. This has the effect of bringing the kissaki up to the right height directly before beginning it's horizontal path.
I asked Harry to look at the three of them and while she couldn't tell the outward difference between 1 and 2, 3 seemed contrived. I decided to abandon that method for now (I suspect it is a Jushin Ryu thing anyway) and keep to method 2. I have to be careful to make sure that it doesn't become lacklustre and I think as I described in a previous post, the timing of sayabanare is very tricky.

Anyway I worked on the rest of the elements of Shohatto and then started working through the rest of the koryu, settling for one form each unless I came across a particularly challenging form. I stuck with Ryuto for about 10 times to try and get this feeling a bit more natural. Again this is a form that has so much content although it looks quite simple in its construction. The final cut is a bit of an enigma as it is supposed to be done mainly one handed and one shouldn't try to reach up with the left hand to reinforce the cut until the sword is well on the way (at least, I think). In any case this last cut has always been a bit unsatisfying for me so I tried varying the size of the cutting arc. Natually, too small and it caused the body to tighten up, too large and it delayed the timing. There was a nice medium that I think I found which was a bit larger than what I normally do and embedded itself nicely with a grounding of the final posture. Speed isn't something I have much of a problem with this form now but try to keep the movement fairly linear instead of flailing around can be difficult. I think that's why it needs so much practice at a medium to slow speed - it's far too easy for the form to become busy.

I carried on through, working through Gyakuto's kaewaza and to the end. I commenced Chuden by doing a quick jump through hayanuki (although it wasn't particularly "haya"). One thing that has taken me recently is the way that Ishido Sensei manages to get his sword out while the body is still quite far back. By making sure that the final forward body movement into nukitsuke is fast he ensures that the cutting portion of nukitsuke is done with the feet in the correct place. If you watch Kasumi you will see this even more. I have been dripping this into Chuden a bit recently, more as a way to challenge myself to get my ass moving.

This reminds me of the importance of the difference between seiza and tatehiza. While I expect most people prefer to sit in seiza given how much more painful tatehiza can be, the practical benefits of tatehiza are huge. Why is this? I think simply because that you are much closer to that very maneuverable position that I will for arguments sake call "iai hiza" with the toes of the left foot engaged with the floor and the right foot placed properly on the floor so that one is propped up and ready to move (similary to the ready position in Gyakuto as the sword is drawn downwards/forwards before evading). From this position it is possible to:
  • Move forwards as in Yokogumo (and backwards in a kaewaza or regional difference)
  • Move forwards and up as in Inazuma
  • Move backwards and up as in Toranoissoku
  • Step back and anticlockwise as in Takiotoshi
  • Turn left as in Urokogaeshi and Namigaeshi
  • Stand straight up to walk as in Torabashiri
  • etc...
From seiza it is possible to:
  • Move forwards
  • Drink tea
Of course I'm joking here, the first four basic forms of Shoden Omori Ryu are there to develop one's ability to turn and cut but you may notice how the majority of the kata from seiza have a forward moving dynamic. From the feet under position, moving forwards and standing up by placing a foot in place under the body is possible but creates an extra movement that is otherwise absent in tate-hiza. As painful as the sitting position can be, it's versatility is the heart of iaido (I believe).

Anyway, over to feedback and control. There is an engineering function known as PID control which forms the basis of complete system control. It is, if set up correctly, the perfect way to control a system. Closed loop control means that the output of a system is used to feedback into the control. A good example is the cruise control of a car; the speed of the car feeds back to the controller and if it is less than the set speed then the controller increases the gas to the engine, if it is greater then the gas is reduced. In fact, the act of a human driving a car has exactly the same set of processes but we tend to ignore the human interaction as it is a) complex b) subject to human decision and c) requirement of someone to sit there controlling it. PID control prevents a) the car spending hours reaching 70mph and b) constantly jumping the speed up and down about the set speed. PID stands for Proportional, Integral and Derivative. Maths geeks will know most of this but for those that actually have a life:
  • Proportional means that the input signal is multiplied or divided by a set constant (as speed in rpm isn't the same as accelerator pedal pressure).
  • Integral means the longer the delay between there being a difference between the set point and the output value, the greater the output signal becomes (if the car takes a long time accelerating up to the desired speed then the accelerator pedal is pressed down more).
  • Differential means that the rate of change between desired output and set ouput determines the next output signal (if the car suddenly shoots off from standstill to 50mph in 4 seconds then the pressure comes off the pedal to stop the speed overshooting 70mph).
The total function of PID is that you get a control system that doesn't overshoot, oscillate or take forever to reach its desired output.

...and what the hell does this have to do with iaido? Well, it's this - doing any kind of movement by a normally functioning human requires careful coordination between input signals, desired outputs and objectives around how fast one wishes to achieve the desired output. Just like picking up a sausage, doing iaido requires this further coordination. Is being aware of this control mechanism beneficial to actually doing the desired operation? Dunno. But perhaps being more aware of how our control control systems are tuned can help us understand how and why some people perform better and worse depending on the person, the time and the environment.

How so? If you have ever trained in iaido in either a small room or close to a wall you may notice how wonderful your beautiful sword sounds as it cuts through the air. You may also notice how your overall form feels better, sharper, better coordinated. Is this just because it sounds better? Maybe not, it's very possible that this very instant feedback is being used by some of the conscious and subconscious processes in your grey matter to improve things like timing and applied power.

I certainly have had the experience of training in a massive hall where the sound of the tachikaze was dissipated almost completely and it felt like the hardest and most overpowered training I had done. In that situation it becomes necessary to rely on other sensory input routes other than aural. Kinaesthetic would seem like a good replacement.

Ok, this posting is becoming a bit long and I will have a "training at Vic's dojo" and "training with Ishido Sensei" article coming up shortly so I'm going to post this and continue this topic as and when I can. Sorry for the delay, been busy with work...


  1. Your engineering feedback analogy is very interesting. My PhD was all about feedback systems in human motor control and the one thing that is very obvious is the the best understood systems are those that are unconscious in the cerebellum, brainstem, basal ganglia etc They are the systems that come into play when you slip on ice and manage to remain upright or prevent you falling over on a moving bus. They are fast, require constant proprioceptive feedback and are low gain systems. Conscious systems, those 'under our command' are far too slow to be anywhere near as effect as the unconscious ones. In Iai or any other physical discipline, we spend a long time 'hard wiring' these conscious corrections into our cerebellum et al.

    Anyway, an interesting observation-again!

  2. Thanks for the feedback. I like what you said about hard-wiring moevements into the cerebellum. I am particularly interested how we use those feedback mechanisms to unconsciously change our technique.