Ah! Oxymoron, you must be a young sprog to be asking a question like that. But to answer your question, I think that you become elderly when you become inactive because of your age. No matter how old you become, you still feel younger in your head, if you know what I mean.
I am 65, I am still active, go for 5 to 10 mile walks, can still climb ladders, fells and mountains (the smaller mountains of course), and yes, i suppose that I am old compared to yourself, but in my mind I don't feel like I am an old codger yet. So don't despair about looking in the mirror every morning, just cover the mirror up, and enjoy a long and happy life.
Jonukas