Physical fitness IS a MUST!! Not for shooting, but for living. Age, injury, and disease ultimately catch us all. The only way to "shoot back" is by working the body. Exercise is a proven, FREE (relatively, running shoes cost money) way to increase the quantity and quality of life. As the old saying goes, "If you can't run, walk. If you can't walk, crawl. But, by all means, keep moving." It sounds funny, but it works in life too. Keeping active keeps you able.
Oh, and there isn't just running. That's my addiction. There's swimming, hiking, martial arts, (all other addiction... guilty as charged.
) and many other activities for everyone. Get up, get outside, get moving... and shooting.