Saw one guy on the preacher curls, he was probably doing 1 or 2 plates short of the whole stack but imagine his arms fully contracted and he would only release it less than a third of the way down, then use his body weight to heave it that tiny bit back up.
Another guy on the hammerstrength iso seated row, same thing, he would bring it all the way to his back, then release it less than a third, then heave it back.
Also another guy doing the rope pulldown for triceps, he wouldn't even extend it all the way down to work the triceps, he was doing rapid fire a third ROM.
I saw this all on the one day, it was too much to bare. Not sure if this has anything to do with it, but no offence, they were all asian.