That phrase really annoys me.
Muscles don't have brains. muscles don't think, and they don't get surprised. They respond to stimulus - to damage.
Cause hypertrophy - eat - they grow, thats it.
It's science at the end of the day.
What you are getting at is the fact that your muscles will adapt - get stronger and bigger - to the correct stimuli, thats why you train. You don't have to jump out on them in the dark or secretly grab a dumbell mid-bench press to shock your biceps; if you understand what I am saying. In my opinion, unless you are steroids, once you get into the whole pre-exaustion, super-setting, tri-setting, drop setting and so on in order to bring your lifts up, at this point in your training... you are on a very dark road.
I don't mean to be pedantic.