That phrase is full of potential trouble.
Since power does not equal work, I think it should say "and" rather than "or". (and no, "and/or", is not a word. "And" is inclusive, "Or" is exclusive, so "and/or" means nothing.)
work = force x distance
power = force x distance/time = the time rate of doing work.
Let's see if you do understand. Is it work that remains constant, power that remains constant, or is it both that remain constant?
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek