In Arnolds Encyclopedia of bodybuilding he says that when doing certain exercises like (I'll just name a few) tricep pushdowns, incline dumbell curls, and upright rows, you should squeeze the muscle at the top (or bottom) of your lift to feel the muscle contract.

Wouldn't doing this burn you out faster and thus cut down on the amount of reps you can do?

Does anyone lift like this?

I always though you should do a lift in one continuous motion without stopping.