Fitness for Seniors (Me)
On days I don't play tennis I do a variety of things, but my primary activity, which I highly recommend, is the Scientific 7-Minute Exercise program that was popularized in the New York Times last May. Based on the theory that short-burst high-intensity exercise is better even than the longer aerobic exercises like running, it is a series of twelve exercises done for thirty seconds with ten second intervals (jumping jacks, wall sit, push ups, sit ups, step ups, squats, front plank, tricep dips, running in place with high knees, lunges, push ups with a rotation, left and right planks). These are done without the use of weights, only a sturdy chair for the step ups and tricep dips, which means you can do them just about anywhere (hotel rooms while traveling).
People who are seriously out of shape will find even seven minutes of this extremely difficult. When I first did it I was in so-so shape and pushed myself through, but I felt it. Since then I have built it up a lot. Some people repeat the series two or three times in a row. I have expanded the length of each exercise so that now I am doing three minutes of jacks, sets of fifty pushups, a hundred squats, etc. When I'm on my game, the whole regime takes me 23-24 minutes with almost no rest between exercises. At the end I am drenched and desperately need a sports drink. (Gatorade may taste like motor fluid but it really works. I never play a serious tennis match without it.)
I am working up to doing this series for thirty minutes five times a week or so. I also keep a set of hand weights and an ab cruncher in my office, so I can do a few minutes of exercise at random moments doing the day. And I walk any time I can. Unfortunately in L.A., that's not much. Basically it means taking the stairs instead of the escalator in the mall parking structure.
So exercise is the key. In fact it's almost everything, especially if you're like me and have little self=discipline about food. The only advice I have in that regard is try to skip dinner once or twice a week. Also, If you're near a Costco, go buy their economy-size packs of frozen blueberries. They're supposed to be some kind of anti-carcinogenic miracle. Put them on everything or eat them straight and you'll live forever -- or at least until next week.
My other piece of advice is never retire. Don't even think about it. Of course, these days most people can't for economic reasons. So that's easy.