This is really a shot in the dark answer and I will be honest in telling you that I am not sure...but based on people I have known, who had injuries and had to lay off training for months...yes, they did lose some, but not that much. Plus, when they got back into training, they gained it back. Six months to recover is a lot better then having to live with an injury you aggravated and will not heal completly. You say your doctor has some exercises for you to do...so it sounds like you will bounce back. I was on crutches for a month when I was 21 from an accident and I remember almost every night taking a tape measure and measuring around my body fearful that I would lose a lot...and finally resigning myself to the fact that there was nothing I could do about it, and in the end I recovered nicely.