Quite an odd question.
It looks that you are a female patient and that is why bothered about,
There is no way to make the shoulder muscles to come back normal or get atrophied.
You can just take a precaution bu avoiding any activity which can strain on the shoulder muscle.
Secondly, when you are not active muscle wise that most of the muscles look near normal.
So it is possible that they will regress on their own if not used forcefully.
Hope this helps you.
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