Kum La Sao (restraining hand)=Chin na is really pretty sophisticated to apply effectively in a combat situation and requires advanced skill to make it work. In my experience though it is not dependant on strength but on leverage and skill and be able to sense the opponent. Also, if your opponent knows counter Kum La Sao...then he will be able to get out. The best man will overcome the not so best one in Kunm La Sao. Not sure about the rest...I would need some examples.
GHD
...ask for Kam
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"Fool me once, then shame on you. Fool me twice, then shame on me"