I go about 5'9. It's possible that my occupation has an impact, but it might just be that you all are soft.It was hard as hell. Lots of hammy strain to get the movement going.
If it was easy I assume that you were either short or you didn't do the movement strictly. 90 degrees and then lift. Not roll the back.
you also might have been using a plastic chair that weighs nothing.
Or a great ass from your glute work.