The larger the womens breasts the more difficult it is for them not to bounce while she moving. You can thank the laws of physics for this.
There used to be a TV program in the UK called Tomorrow's World featuring recent developments in technology. I still vividly remember one episode from the late 60s or very early 70s in which a new piece of satellite rest equipment, a large "shaker table", was demonstrated.
For this demonstration one of the show's regular presenters, a rather well endowed woman, stood on the table while it was vibrated vertically. The frequency of vibration was slowly swept from very low, less than i Hertz, up to the low audio range.
As the frequency swept past her natural boobs bounce frequency this resulted in a most memorable demonstration of resonance effects in ***** harmonic motion - in particular the large amplitude of the induced motion at the resonant frequency of "the system" and the way its phase shifted.
As an undergraduate phsyicist at the time I greatly appreciated this demostration of one of the laws of physics.