The other day i read a forum thread considering whether regular exercise is any good if one does not continue adapting. My first reaction was, "Stop overthinking it and go out and do something!" Seriously, any excuse right? Let me sit here on the computer and check all the known facts before blah blah blah. Say you decide to do a 5k three times a week, for the rest of your life. Chances are, you will start going faster- this is an adaptation. Or, as you have an allotted time to fill with exercise, you start to go further, also an adaptation. Or, you decide running is boring, now you are going to swim, lift, Zumba whatever. Changing your activity is yet another adaptation. If the worst case scenario is that you continue to run or walk a 5k three times a week for the rest of your life, so what? You will most likely still be better off then you were sitting home online trying to figure out if it is really good for you or not. Sometimes you have to get off your butt and do something.