I fully realize that this post will probably more info than 99% of the people want...but in the interests of laying it all out here goes.
Generally ALL asian arts train a specialized way of using the body, which produces an odd way of generating force.
Most demos in arts are shown to isolate and illustrate this skill : From Aikido's unbendable arm, Ueshiba's "push on my head, see you can't move me" tricks, to various Chinese arts showing guys getting tossed and bounced around.
The various arts are simply different ways of developing this skill.
Putting it down simply, they all train Ki/Qi/Prana (all those terms are equivalent, anyone who says differently probably has no skills), to produce Jin/Kokyu-ryoku/Shakti.
(Ki/Qi is a physical, trainable trait, and interchangeably and frustratingly either refers to the fascia that connects the body as a unit, or the specialized use of inter-abdominal pressure)
Dantien/tanden is a trainable area comprising the core muscles, spinal erectors and pelvic floor, and incidentally is where the fascia of the body, which ties the body together is thickest.
All the arts, Aikido, various Koryu, Karate, all the Chinese arts, typically try and train the dantien/tanden, and some use the tanden area to control the entire body (think of a large balloon man, if you want to control the limbs of the balloon man, you move the middle, and its the stretch that moves the arms, not local muscle).
This kind of body mechanic produces the ability to generate disproportionate amounts of force for the amount of movement used, and also involves the clever use of physics (and not the kindergarten level of physics seen in Judo)
In short...if you're serious about training this stuff, find the best teacher that teaches this stuff directly.
They aren't woo-woo skills, they can be trained, there is a certain IQ skill required to figure it out, and its not for everyone.
Personally I train at the Aunkai under Akuzawa Minoru, who's 160cm, 64kg and can throws around guys twice his weight with ease, but I train there because of the direct instruction offered.
Hope this post my shave a couple years of wasted time for some.