You could make a script that would write out specific body parts, or you can chop them out with an editor after it's saved.  There isn't any built in way to repeatedly save only specific parts of a pose, it's either everything for the figure (which includes magnets in V4, which is very bad, and a lot of other junk besides) or you have to carefully go through the hierarchy each and every pose.  You might want to look at "PoseWriter Premium" included in some versions of Poser, if you have it.

I got it included with Poser 8 (Scripts -> Netherworks)

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