When I started running, my left foot seemed to overpronate a little, such that the recommendation of the running store experts was "mild stability shoes."
"Okay," I said. "Show me your mild stability shoes and I'll pick some out and be on my way."
Since I wanted lightweight trainers, I ended up in Asics Gel DS Trainers. Nice lightweight shoes, really, but soon I developed ITBS, and then the outsoles wore through to the midsole of the Trainers in less than 300 miles, and I was looking for other options.
I began to research ITBS, and discovered essentially that the most effective way to deal with it, long term, is to strength the core and hips and get a better handle on your running form. I've written extensively about my research and treatment methods for ITBS on my other blog (http://www.be-fit-now.com - far more technical than this one). So, I set about strengthening my core, my lower abs and glutes, my "hip abductors," and also began to study up again on running biomechanics and running form. Soon, I was teaching myself ChiRunning.
It wasn't long and the combination of improve strength in my core and hips and my new running form that I noticed my feet had straightened out when running. No longer did my toes have a tendency to point outward. I had trained myself to engage the appropriate muscles to straighten them out. Further, my feet did not overpronate as much while running. Sure, if I relax and walk around, they still have a tendency to want to do so, but when I run, they now seemed trained to swing straight and true.
Another thing that changed was that my knees had stopped flexing and rotating inward and rubbing together like they used to. This despite a switch to a neutral training flat! Pretty cool. So, the recent research that points to weakness in the muscles of the core and hips that control what our legs do while running and walking as the source of some overpronation and other correlated biomechanical problems appears to account for my problems.
A lot of people latch onto success stories like this with a sort of religious zeal, and assume that results like mine would apply more generally to everyone. I'm a little more cautious with my inferences, however. I'm a sample size of 1. You can't conclude anything from that with confidence. Anyway, there are people whose feet are so flat and who overpronate so severely that it is unlikely that their entire problem can be solved simply with core and hip strengthening or simple changes in their running form.
I think for a lot of people it is certainly true that we pick up running in our 30's or 40's after years of, well... not running, and some of the muscles we need to support good form have simply atrophied, or gone soft. Not only that, some of the nerves that coordinate what our muscles do during our stride become uncoordinated with disuse as well. That's why after years off from running, you feel so floppy and uncoordinated when you finally try it again. It feels unnatural until you begin to get stronger muscles and nerve/muscle (neuromuscular) coordination. Our problem at that point is that because so many key muscles are weak, our form is not very good, and we use different muscles, preferentially and my theory is that the patterns and balance of strength and coordination in our running muscles therefore re-develops in sort of an off-kilter or unbalanced fashion, leading to stress on some muscles and tendons that go beyond what they were designed to withstand, or perhaps are able to withstand in their relatively weakened state.
If my theory is correct, then making the decision to begin running again should probably be followed not by strapping on some running shoes and heading out the door, but instead by some assessment of core and hip strength and a couple of weeks of good core and hip exercise to get the muscles you need to support good running form on the road to fully recovery from the inactivity they have suffered on the couch. During that time, most people would be well-advised, I think, to learn what they can about running form, so they can attempt to put some of that advice to use when they head out on the road with a new pair of running shoes.
Speaking of running shoes... My personal philosophy is that people working on their strength and actively improving their running form should probably go with a shoe that offers slightly less stability than they think (or are told by experts) they need. Over time, this can help strengthen some of the muscles and tendons needed to run without as much excess support.
In reality, I have run into people who instead choose to go with shoes that are MORE supportive than indicated by the degree to which they overpronate... If a little stability is good, then even more must be better, right? Wrong, I fear! Pronation of the foot is key for absorbing some of the shock of running, and is quite normal. If you wear shoes with more stability or motion control than you need, they may be so supportive that they reduce the healthy, shock-absorbing component of your pronation, and result in greater shock being trasmitted up the leg to the knee and hips. There, this extra shock may contribute to a handful of acute injuries or overuse injuries/syndromes.
So, back to my original question... Is it up to you, or up to the shoe to solve problems with your running biomechanics. I think the reality is that it's probably up to the runner when biomechanics are only mildly off-kilter, but when it's severely so, it's probably up to both the runner and the shoe. I'd caution against anyone relying completely on a magic shoe to fix the difficulties they have while running. I think that's a recipe for pain and will probably lead to premature retirement from the sport for many people.
Like many things in our body, the prevailing paradigms for years have said our physical structures and movement patterns are completely genetically determined, but recent results have led experts to questions this. It turns out that our bodies are capable of adapting to some degree, both in form and function, when they are required to do so. We can learn new motor patterns, and improve our gait through learning, then training - at least to some degree. The evidence of our ability to improve our physical form at various tasks and the body's ability to adapt to these changes over time so they become second nature has always been in front of us, if we chose to look for it. I'm going to get in trouble for saying this, but girls who at first threw like... well, girls... have learned to raise their elbows and throw things more effectively (I have been struck by things thrown at me thus). Just as a dancer or a gymnast can practice maneuvers that at first feel unnatural or uncomfortable until they are second nature, we can also improve our running through practice. It's worth a try anyway for many of us.