I have done this in several pump classes of old and one instructor would always ask us to imagine a glass of champagne was stuck on the sole of our shoe and we had to raise it up reading for filling. This instructor often appeared hungover too...no judgement, I'm just saying :)
Anyways, I did two sets of 30 of these on each side and I have to say my butt was screaming. If butts had tear ducts they would have been weeping too.
And that would be very creepy indeed...a crying butt, ewww...suffice to say, this move really seems to target my glutes and banging out 30 one after the other was really difficult. I had to take a couple of breaks in there so my entire butt didn't fall off with shear exhaustion.
I realise my butt falling off and crying on the ground is an extremely sad image for everyone so here is a positive ending...
from chin up sunshine