Dmitri wrote:"Up from the ground, controlled by the waist and out the hands." is a mistranslation AFAIK.
It's not talking about anything "coming up" from the ground, etc.
It says, "jin is rooted in feet, developed in legs, controlled by yao and expressed through hands/fingers"
'yao' is the "small of the back" (again, AFAIK), including pelvic area, upper part of the hips and lower part of the waist.
FWIW
In the end, it's just another "phrase from the classics" -- meaningless without a way to "implement" it in real practice.
It's a catch phrase that has been taken completely out of context.
“其根在脚,发于腿,主宰于腰,形于手指” is about using Lian and Sui (Link and Follow).
It's how one 'Sheji Cong Ren' (Give up (to link) and yield to the opponent's attacks (to Follow)).
After one Sui (Follows) then they could counter-attack using the power of the Dantian and Spine.
Wu Yuxiang's best student, his nephew Li Liyu wrote some better stuff on the topic of 'Sheji Cong Ren'.
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