Then I bought his conditioning DVD from Tsuami and watch him do the jars and watched him poke around on Joe Graziano as he did the jars.

And I think, I get it now.
Now - that might seem a silly thing to say after 10 years in Uechi. But I don't think I ever fully, understood what the jar training was about. That doesn't mean my teacher didn't show me and tell me, I just didn't get it. I not sure I even could have understood it until a couple of years ago - simply because I don't think I knew my own body well enough to find each and every muscle and feel every little tendon.
Sanchin training with nigiri gamae is a very old and very specific training. The teacher touches a muscle to bring the student's attention to it. Then student then adds that muscle to the group of muscles being activated. The jars enhance the gripping and grabbing, help remind the student to keep their shoulders down, and with added weight - add additional stress to the overall body - a body that is already being asked to engage itself at 100%.
I've had a set of jars for a few years and I've used them...but I don't think I've ever used them the way I have in the last week.
I don't know if the jar training is Okinawan or Chinese and I honestly don't care. However, I am starting to believe sanchin is really two forms.
In with the jars training (sanchin nigiri-kami/kamae/game/) - the student is asked to activate 100% of their muslces 100% of the time. Hard, hard, hard qigong. As hard as humanly possible.
In without the jars sanchin (sanchin kata) - the students starts the half hard half soft training - everything can't be hard 100% of the time. Then you go along the Uechi continuum and get to sanseiryu - where things are soft until they need to be hard. (Soft doesn't mean floppy - it means a baseline)
I'm also deepening my understanding of why the two parts of the sanchin training have equal emphasis - even though that doesn't mean equal time.
And I've got a question if anyone could share the answer I'd be grateful.
In watching, in person, Mr. Narahiro Shinjo, Mr. Gushi, Mr. Toyama, and Mr. Gaziano do some or a full kata of the jar training - at some point while on full activation they all did this thing of streching the neck around - some with more motion than others.
Why?