Now, I have been doing armbars for well over three-fourths of my life and never once when I leaned back has the mat disappeared out from under me, so I think you are pretty safe in assuming it will still be there.
Maybe some people are afraid that they will hit their head as they arch back. In that case, just do the same thing anyone does when trying to prevent hitting the back of their head on the mat - tuck your chin.
Never, ever, ever when you are applying an arm bar and leaning BACK do you let go of the arm with either hand. Lock it to your body with both hands and arch.
There is ONE arm bar Ronda does when she is going FORWARD across the opponent's body and she lets go with one hand and reaches in front of her. I don't do it that way and she says she does it to stretch her opponent out.
If you want to see the ONE circumstance in which I think it is possibly maybe okay to let go of the arm it's on page 38 in Winning on the Ground.
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