Ground Reaction Forces for Rotational Patterns 101
if you try to create a rotational movement like a med ball pass standing on a slippery surface, why do your feet move in the opposite direction of the intended rotation??
you use ground reaction force to produce a force-couple/torque which is translated from the feet-ground through the legs to the pelvis to initiate the rotational motion which in turn produces the subsequent coordination to toss the med ball
ground reaction force is the force that is equal and OPPOSITE of the force applied by you into the ground through your feet
when you stand on "sliders" you aren't able to create friction, so the ground is not able to "push back" ... the legs twist in the direction you are applying force