The very first thing I do when I load a figure is to turn off IK. For those figures I use a lot, I resave them with IK off, then in a text editor I edit the names of the leg IK chains to "Right Leg" and "Left Leg". Next time I load them IK is off.

Poser automatically applies IK to any chain named "RightLeg" or "LightLeg", putting a space before " Leg" stops Poser doing this, but the figure needs to be saved with IK off first.