Last night I was working with a guy, he was doing barbell sumo deadlifts for the first time. The first couple of sets were a bit rough as he learned the movement. By the third set he was looking smooth and strong with it, though just did 3 reps.
I gave him a fourth set, told him to do 3 reps again. By the 2nd rep he was doing it so smoothly that I said, "You're doing well, better make it 4 reps."
"FCK YOU!" he cried indignantly.
I laughed.
He did 4 reps, put down the weight.
"Okay, keep your back extended as you lower the weight... well done."
I patted him on the back.
"See, I knew you could do 4 reps."
"Get fcked," he said.
This is in contrast to workouts in the Army with PTIs yelling abuse at us, or Biggest Loser-inspired trainers who yell at their clients. I think I prefer it the other way around, trainer stays calm, the client does the swearing.
So here's my thought: In a bad session the instructor yells abuse at the client, in a good session the client yells abuse at the instructor.