If you like rocking chairs, Aeron is waaay more of one than Leap. Leap's seat pan slides forward when you lean back so you can't rock on it.
if you have/have-had/it's in the family .... lower l4/l5 back problems then maintaining good core strength back+stomach muscles is essential -
which is where rocking kneeling chairs force you into an active position, not permitting you to slouch ... and if you rock forward have to move upper torso back and vice versa.
these feel like flying initially, really novel, unfortunately the sensation wears off as the body adapts
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