There is also a lower threshold over which no permanent injury occurs (yet) but which makes workers borrow upon finite reserves of endurance which eventually (s

There is also a lower threshold over which no permanent injury occurs (yet) but which makes workers borrow upon finite reserves of endurance which eventually (soon) need to be replenished with interest. So if you even it out over time workers are actually less productive. This is known in the gaming industry as the crunch mode, and it's what I would consider "over 100%". Permanent damage occurs if you accumulate too much interest. Both thresholds vary per individual - known as stress resistance. IMO, any mention of it as a quality in interview is a big no-no.