Pratice good fitness to play your sport -- do not play your sport to be fit.
A personal recommendation. (Senior Golfer)
Fitness is nothing to fear. The best way to become fit is to do what is comfortable for you. Swimming one to two miles a day is probaly the best to become fit, and improve your golf game. Some may pefer a 5 mile run, or a 25 mile bike ride. All these can be extremely helpful, but for now not in my plans. Still there are ways to improve fitness without a lot of effort. You may ask how I know this.. or maybe you don't care, either way I'm going to tell you how I know. I went through a cardilogy rehab. The methods they offer where all easy, but I tried to make them hard. My perception has always been that if my exercise was not causing me pain then it wasn't working. Sad that it took science to show how wrong that perception is..nuff about my background to be qualified to offer others suggestions of things that will improve their fitness.
Much is stressed about the best methods of creating the best golf swing. Very little attention is paid to the person's physical abilities.
Cody, I think you could be the perfect therapist to assess a person's physical abilities and areas for improvement.
Here is what I found through my personal research.
Aging will restrict our range of motion, but only if we allow it. The solution is not buying into lighter clubs. The solution is to do some very easy excerises recommended by Dr. Cody Johnson following an accessment of "your" physical strenght and weaknesses.
This for me has been a "Fountain of Youth" experience.