Not much but thats where the resistance part comes in. Remember that an opponent isnt going to stand still with his hands down like in the demonstration. He has his guard up. He is going to move to defend and to launch his own attack on you. On top of all that you have to contend with the adrenal dump that has been placed upon you in response to the present danger. This often leads to less than precise hands and thats something you need when striking to a resisting opponent. You must be fast and accurate and under pressure it just isnt a high percentage move.
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"When I let Go of who I am, I become who I might be."
Lao Tzu