We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
It has become a casual consensus that exercise, or at least daily vigorous movement, enhances one's immune response.
Anecdotally, it looks likely. But the catch is that it's the most fit people who do an hour or so most days, so is it causality? Statistically, fitter people are best prepared to deal with the attacks of nature: better disease-resistance, better healing, etc.
People with physical jobs do not need to think about it, but most of us do. In a way, daily exercise is an attempt to recreate a bit of what humans were built to do.
I feel that exercise (The Maggie's Fitness for Life program, especially) has the main goal of maintaining functionality and vigor for as long as possible. Sure, looking good matters too, in life. Nutrition for weight, exercise for strength.
I've lived most of my life in a rather physically demanding environment. Maintaining physical conditioning is not too hard until you get into your 60's, at least for me. After that point it does seem that every old injury tends to manifest itself into aches and pains on far more numerous occasions. But, still, it is worth those physical reminders as we move along with life. Don't forget the vitamin D, C, and some zinc.