Interesting comment. It's so obviously immoral to me, that seeing someone question it has me considering how morals are instilled in other cultures / generations.

I don't mean to frame this from a moral high ground either. Just mildly curious.

TENS isn't muscle control and what is described doesn't seem to be voluntary but imposed (and economically coerced) use of physical pain as a means of correcting workplace errors.

It still breaks individual autonomy, probably.

It’s not external muscle control, that’s not what a TENS unit does. OP is describing using painful electric shocks to punish a worker for mistakes or for going off-task, i.e. brutalize workers into performing with machine like efficiency.