First, I've always believed in and advocated exercise no matter at what time of life or the mental games I have to go through to keep myself on an exercise program. ;)

Second, early last year I started a light calisthenics set immediately before my morning guitar practice...basically the first thing I did when I got up. The set included pushups and believe me it isn't a lot of pushups. The entire 'workout' takes 15 minutes.

I noticed that my fret hand feels stonger and there are less aches and pains both in my hand and in my shoulders. I can't attribute those changes to that specific exercise because I do other things that relate to conditioning and flexibility but I think it has helped and I suspect it has helped a lot.

Like all things, playing guitar requires some level of endurance, strength and flexibility. And just like all things, exercise, especially targeted exercise, is helpful throughout life and increases in importance as one grows older.

If anyone is having aches and pain problems one of the first things they should look at, IMO, is their conditioning as it applies to the activity that's giving them trouble.