As the author, I want to note that I’m way more skeptical of my earlier explanation.
(Accordingly, I’m less confident of my current explanation too!)
I’m pretty sure the movement cannot work if you vice grip my upper arm such that it can’t move relative to my body (or to the ground). The elbow must be free to rise a bit.
Sometimes I’ll demo the trick by letting people fold my arm, asking them to continue applying as much pressure as they like, warn them that I’m about to start straightening my arm, and then just do so. It’s close to effortless for me. But when I do it, my whole arm goes up first. I then lower my arm again once it’s straight.
The lats might be closely involved, but I don’t think that’s the main issue. I haven’t noticed any effect whatsoever in terms of unbendable arm strength based on lat strength.
Also, once someone who’s vastly weaker than me gets the “click”, they’re able to (sometimes) defy me regardless of how much muscular strength I put into it.
So I’m pretty sure it’s some kind of leverage trick.
My best guess right now is somethingsomething redirecting force between the incoming hands into each other somethingsomething.
I use the same feeling to hold very heavy objects when I put my hand on a table. Like hanging a heavy grocery bag on my elbow with my arm straight and my palm up. I keep it suspended by letting the bag press the back of my hand into the table. IME I’m not so much fighting the bag’s bending my arm as I am just… reaching. If you make the bag heavier, it presses my hand harder into the table. That’s it. It’s not relevantly harder for me to keep the bag suspended.
See also Proper posture for mental arts, which also mentions the Unbendable Arm and explains how it works biomechanically, namely via the latissimus dorsi.
As the author, I want to note that I’m way more skeptical of my earlier explanation.
(Accordingly, I’m less confident of my current explanation too!)
I’m pretty sure the movement cannot work if you vice grip my upper arm such that it can’t move relative to my body (or to the ground). The elbow must be free to rise a bit.
Sometimes I’ll demo the trick by letting people fold my arm, asking them to continue applying as much pressure as they like, warn them that I’m about to start straightening my arm, and then just do so. It’s close to effortless for me. But when I do it, my whole arm goes up first. I then lower my arm again once it’s straight.
The lats might be closely involved, but I don’t think that’s the main issue. I haven’t noticed any effect whatsoever in terms of unbendable arm strength based on lat strength.
Also, once someone who’s vastly weaker than me gets the “click”, they’re able to (sometimes) defy me regardless of how much muscular strength I put into it.
So I’m pretty sure it’s some kind of leverage trick.
My best guess right now is somethingsomething redirecting force between the incoming hands into each other somethingsomething.
I use the same feeling to hold very heavy objects when I put my hand on a table. Like hanging a heavy grocery bag on my elbow with my arm straight and my palm up. I keep it suspended by letting the bag press the back of my hand into the table. IME I’m not so much fighting the bag’s bending my arm as I am just… reaching. If you make the bag heavier, it presses my hand harder into the table. That’s it. It’s not relevantly harder for me to keep the bag suspended.
Again, no lats.