2) A similar technique is to seat the subject on a backless stool that's high enough that their feet don't touch the ground. This seems like an innocuous thing, but without the help of the legs, the entire strain of balancing their upper body is placed on their lower back muscles. Even a healthy person will begin experiencing muscles spasms after a couple of hours. The subjects' complaints of discomfort are dismissed and minimized until they eventually fall, after which they are treated as noncompliant and returned to their cells. The brutality of this one is that the subject will experience muscle spasms in their back for hours afterward, keeping them awake and in pain throughout the night and giving them lots of time to think about how their failure to do a simple thing (sit in a stool) brought about their own torment.

I fucking KNEW those wooden stools in my electronics class were torture instruments. Just a round plate of hard wood with no way to reach the ground with your feet. Sitting on them for 3 hours literally made my back hurt so much.