Can the autopilot (or stall avoidance system?) of the B737 MAX 8 be overridden by sheer force? A New York Times article from today about the Lion Air Flight 610 crash claims that in order to control the airplane the pilot


  could have braced his feet on the dashboard and yanked the yoke, or control wheel, back with all his strength.


Thanks to T.J. Crowder's comment I realize there is not only the autopilot but also a (new?) stall avoidance system installed on this new line of B737s. 

Is it true that either one can be overridden by a simple application of sufficient force to the yoke? If so:


What is the respective underlying mechanism for the systems? 
What force would be necessary, respectively?
Are both systems designed such that they can be overridden simply by applying an unusually strong force, or would that be just a violent and "unofficial" way to control the yoke despite the systems' best efforts?1


I understand that the main flight controls of this recent incarnation of the Boeing 737, the MAX 8, are still hydraulic. Does that play a role in the "override by sheer force" possibility?


1
A design which would allow a pilot to eventually control the plane just by applying excessive and unusual force (as opposed to perform a complicated series of button presses and/or touch screen actions to disable either system) would in my opinion make a lot of sense as a "panic mode".
I'm not sure of the full story here, but if you pull the controls of a 737 while the autopilot is engaged the autopilot will trip and the pilots can fly the plane manually. This requires about 25 lbs of force.

There is also a button on the yoke where you can disengage the AP. So if the AP was controlling the plane and going into a violent descent the pilots should have been able to cancel it by pulling the yoke or pushing the button on the yoke or the mode control panel below the windshield.

And no, the controls being hydraulic doesn't play a role in the "override by sheer force" possibility.

Edit:


  The autopilot servos are limited to 25 lb of force for single channel operation. Separate force sensors measure pilot column input and the autopilot will disconnect if the force applied by the pilot(s) exceeds 21 lbs.


Source