Lowering the bar faster to get rebound is tempo as the speed changes. And opinion on this is different to as we are finding out.Rebound is not tempo.
One persons perfect form is another person's cheating as we are seeing perfectly clearly here!It's allowed, meaning nobody is going to arrest you. But once you lean, you're no longer doing the same movement, you've taking load off the biceps by changing the force curve and leverage points.
Failure is when the task can no longer be completed with the proper form. Crystal clear.
I am just interested in what the researchers went by. So i can judge it against my opinion.