Hi there

As I was just reading my text book I came across a sentance I don’t quite understand..

Its talking about protein degrading even though it seems like a person is doing no activities that need to require replenishment as there is a constant need for quality protein in order to maintain the body’s structures..i get this part but then it goes on to say athletes are painfully aware of this fact. they must train constantly and get out of shape quickly when they stop…what do they mean by this?–

Thanks
biology_06er