I have what I believe are clinically referred to as flexible flat feet. When standing almost my entire foot comes to rest on the ground, but when I flex my foot, a natural arch appears. Or at least they used to. Since I started running in minimalist footwear I have noticed that the arches of my feet have slowly become more distinct. I would show you in a pic but, I think that one pic of my ugly feet is all the web can bear for now. You'll have to take my word on it.About the time I started to notice the strengthening of my arches, I also noticed that when I stand, my ankles would have a tendency to kind of crash in medially which would flatten out my feet. This has lessened quite a bit and I think is one of the central causes of my flat footedness. Again, at least it used to be. Over the last month or so, my ankles have gotten stronger and my feet have started to straighten up. This has not been without some teething, however. My ankles, particularly my right ankle has been pretty cranky the last few weeks as the ligaments and tendons on the medial side have caused me various levels of pain as I have worked them in ways my body is not accustomed to. In particular, I think that some of the tendons that articulate my toes have been especially cranky as I have experienced some pain running from about my ankle, wrapping down to the underside of my foot by my arches. This makes sense as these muscles and tendons now do the work of absorbing the shock of each stride as I run. Nothing has been too awful and I have taken the same approach to my ankles as I have to my calf muscles when they have felt a little overworked. I take 3-4 days off and let everything heal up before I go running again. And everything seems to be good. On my last two runs I have worn some elastic ankle braces to provide some compression and to give my arches a tiny bit of flexible support so my muscles don't have to do all the work. This seems to have helped. It feels a little like wussing out when take a few days off like I have, but I remind myself that, before August, I hadn't run in almost a year and I'm loading up some of my muscles in new ways. Given my current not-inconsiderable weight, I think the caution during this early period is well worth it. Considerable research conducted by the U.S. Military on flat-footedness and running has indicated that people with flat feet aren't any more likely to suffer running injuries than those with normal arches. So, in that respect I'm not really worried. But I think it's somehow telling that when I give my feet the freedom to work as natured intended, my arches get higher and stronger. I know I'm not the only one who's experienced this so I feel, strongly that this connection is something worth looking at. I wonder if there's any sports medicine research being done on this?