Think of the items I’m about to discuss—flexibility and strengthening—not in either/or terms in relation to your running, but in terms of “yes, and ... ” That is, they’re not replacements for running, but a form of insurance policy that will allow you to better pursue and enjoy your running at whatever level you choose to. Even if they don’t improve your performance—and they almost certainly will—when done correctly they’re going to make the simple act of running feel better, especially the older you get and the longer you’ve been running. Most of these activities are easy to sneak in throughout the day in little clumps of activity.