A 1rm effort is what it's called, it's the maximum you can lift once. You recruit every motor unit available at that time i.e. slow (type1) and fast (type 11). It's the type 11 that are mostly doing the effort because these fibres are stronger.

Another quite good thing about using heavy resistance is that you train the type1 muscles which maintain good posture.

The irony is in the name Von from now on we should call them type1 and type11 fibres and then the confusion will end.

Von, I'd bet the makers of that machine don't even tell you to work at even 50% of your 1rm. I can understand the logic, once your used to using it, working relatively heavy then going lighter and faster.