I've been reading a book that's been around a while called Younger Next Year. It was recommended to me by a client, Jim Holland, who's an age mate and in great shape. He told me he'd given copies of it everyone he knew one Christmas as it had changed his life. Life-changing books are often a good recommendation, if nothing else to see what the other person is up to.
The basic premise of the book is that if we aren't growing, we're dying. That is, if we stop moving, our bodies slowly close down and move towards hibernation and decay (muscles atrophy, organs don't function well, we don't slough off old cells and cancer can start). This is a very simplistic summary of several long chapters, andt of course it's a variation on the age-old move it or lose it. The book is highly unrealistic in some ways (the authors advocate getting in shape by taking a month off and spending all day each day skiing), but the idea is sound. Get moving or become infirm.
I got serious about getting physical when I was 33, in 1980. My boyfriend at the time was a runner/jogger and he encouraged me to get moving to stay slim and be healthy. It took me a few weeks to get the hang of it and while I never loved it, I did feel better. In fact, for the next 10 years, running was a hangover treatment for me. Then when I got sober, it was a way to deal with extra time and restlessness so I kept at it. Eventually I shifted to walking as my ankles and hips got older and didn't care for the pounding on the pavement.
I have exercised rather faithfully for the last 33 years. The only long period of time that I didn't, curiously enough, was the month I spent in the treatment center, which at that time had no exercise problem at all. We walked two miles once a week.
At the same time that I am disciplined and faithful, I am not athletic. But I do not want to be old and infirm. I want to old, reasonably firm, and reasonably fit.