Re: Posture in Iwama Aikido
Since it is (amongst others) my posterior on the line (so to speak) then I will put in my two yen's worth. Having your pictures out there on the net does leave you as a sort of sitting duck..
Sorry, I couldn't help myself - too much coffee!
By the way, we Iwama folk refer to it as the Iwama Duck :-) So we are well aware of the position as well as the problem.
I can't believe I am writing about my possible protruding posterior on Aikiweb :-)
There's always a first time for everything!
The position we are talking about occurs when you engage the front hip - and this movement becomes over-emphasized.
In aikido as we learned it in Iwama, when striking or thrusting forward weight distribution should be slightly forward, and the front hip is engaged, to transfer energy forward and outward, so slightly more than 50-50 weight distribution is called for. The front foot should be more weighted than the rear at the intended time of impact, but you should at all times be in a posture from which you can move immediately in any direction without having to re-distribute your weight.
Structural integrity is very important: a nice, clean line in the body from ground up to the head with a slight forward inclination is what we should strive for, to channel energy outwards and forward.
The problem occurs when you over-commit and your posture "breaks" from your waist up, causing the upper body to tip forward, and thereby disconnect from your lower body. This often happens if your stance is too upright (feet too close). This is when you end up with your rear end sticking out.
In the old days (1960s-1970s and early 80s) a very wide stance was used, with quite a lot of forward inclination (much like the diagram pictures of old bayonet techniques shown on this thread). .
This stance is strong, but it locks you into a position from which you cannot move unless redistributing your weight. My first Sensei - Takeji Tomita Sensei (based in Stockholm, Sweden) - told us that this deep, forward-leaning stance was based on you as uchi -tachi or uchi-jo, committing fully to your attack. Uke-tachi or Uke-jo (the role of sempai/sensei) could assume a more upright, mobile stance, as this was the more advanced role in weapons training. In the old days the kohai would only be allowed to be the attacker for years, before progressing to the defensive role.
If you notice O-Sensei in the old films, he is almost always in a quite natural stance during his execution of techniques, also in his zanshin at the end of techniques, be they tai jutsu or bukiwaza.
I noticed that Saito Sensei also went from a quite deep, forward-leaning posture in the 1970s and 80s into a more natural upright posture later on. I see this as a natural progression in Saito Sensei's own training.
We were also told in the 1970s and 80s to keep the rear leg straight (this killed my back for several years). Noticing Saito Sensei's slightly bent rear leg when I began training under him in the mid 1980s, I tried to assume this attitude in my training and found my back appreciated the change quite a lot.
So to sum it all up: structural integrity should by all means be kept. We do try to engage the forward hip when striking and thrusting forward, but overemphasis of this position causes the aforementioned affliction - quack quack...