It's when you have coliseum matches in Aris.
every time a tapping QTE come up I could never fill the bar. And to be clear it is not from lack of trying because I have tried. At most I could only ever get it halfway before timme runs out.
During the fight with Elise it doesn't matter how high my brawn is, the gauge doesn't increase. The highest (armor included) is at least 17.
With the clutchmates there is a bit of a difference, but it didn't change the outcome. By this point by including armor collected I had at least 30 brawn.
So I don't know if the stat is low for these points in the story or if the requirments for completing that particular QTE are just ridiculously high.