How to keep muscles from atrophy?

when I got ground up in a car wreck, my physical thereapist had me doing some pretty lame stuff, or so I thought. I asked her what good is squeezing thes ball doing? and doing toe-extensions with like a five ounce weight? and she told me that almost any activity will help from your muscles from shringking-now that's over a six week period, if you are laid up for a couple months, then you're going to experience some muscle attrition. but, a few weeks? just do whatever exercise you can to keep good circulation in the nuscles, even deep breathing exercises will help in this regard. good luck, and a speedy recovery to you.