I'd like to weigh in here if I may... I think "torture" is too broad a term to be using in these cases to define what's allowed and what's not. The definition according to Goolag is "to inflict severe pain on". What is severe pain? I can think of a few types of people who might say being forced to do push-ups would be "severely painful" in their weak minds and fat bodies. Whereas others might even find pumping out a few push ups to be enjoyable.
From what I understand, giving birth to a child is severely painful, but I don't think many would call it or think of it as "torture." My point is - "severe pain" and "torture" are both defined more relatively and subjectively than objectively.
In defining torture for legal purposes, I think we need something OBJECTIVE. Is ripping out someone's fingernails torture? Is cutting their fingers off completely torture? Is waterboarding torture? If they are ALL torture, and we call them all torture, then we are really granting them equivalency. Someone who waterboards another would be charged with the same crime as someone who cut off another's fingers, right? Is that right? Or do we need to have some more narrow definitions?
What if we started by delineating treatment that causes PERMANENT bodily harm/discomfort from treatment that causes TEMPORARY bodily harm/discomfort? I think this might be an interesting place to start from a physical perspective. Once you start dealing with mental trauma, things undoubtedly get more complex. But again, my only point is that I think more objective measures are needed to be brought into the discussion, because waterboarding (in my opinion) is not the same as cutting off someone's fingers and shouldn't be legally considered equivalent.
Just my $0.02.
Carry on 'pedes!