I can’t watch the video at the moment, but I’m of the understanding that the manual wheel actually easily overpowers the electric trim motors—-that it is simple to stop them from spinning and not to difficult to manually spin them as required.
In the video there is a suggestion on how to hold the wheel without breaking your wrist, so I assume it's not too pleasant to do. They also manually spin the wheel and it looks quite hard and slow (the monitoring pilot alone, which is using his left hand, can barely do it; when the flying pilot helps him with his right hand things go better)
I doubt that there would ever be need to physically overcome the jackscrew motor (trim motor), as there is an electrical cutout switch in ready reach. The issue the GP discusses is when due to whatever reason the trim runs away (electrical or otherwise), the 737 has two physical wheels that the flight crew can turn, _OR CATCH_ while it is turning. That is like stopping a spinning bicycle wheel by grabbing it. It is physically dangerous to the crew member.
I wouldn't say "easily": at some point in the video the guy on the right tries to trim manually but fails -- it only starts working when the guy on the left starts helping him.
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