It never fails to amaze me just how many people rely on orthotics, or 'air' shoes, to reduce back pain, correct posture and lift collapsed plantar arches in their feet. Not surprising, seeing as this is what most chiropractors and other physical therapists recommend. The trouble with doing this is that it is mercly covering up a rather significant postural deficiency, and not actually rectifying it in any way. Remember that our feet are often the only contact point we have with the floor and absorb much of our weight, plus the effects of gravity, so their positioning affects everything above it to some degree.
Nothing that we can 'do' to the body is ever going to be as effective as what we can do 'with' the body, and by this I mean that realigning the skeleton and rebalancing tight or weak muscles will always be effective than manipulating it into certain positions or putting it under this lamp or that scanner.
The type of footwear we all wear, particularly for training in, does not help either. We're all bouncing about on inflated soles which, while giving us a spring in out step and feeling comfy, are actually not that great for our feet at all because once again they allow our feet to become 'lazy' and weak.
Take a look at your own feet. Do you have calls on the insides of your big toe? If so it's very likely that your feet pronounce (collapse in) which probably means your butt's not working like it should. Do you have a good curve under your arches, or are your feet as flat as pancakes? If the latter is true, maybe it's time to put your orthotics to one side and actually start correcting your feet. We can do this just as we would correct any other collection of muscles; by training them.
A really easy and simple way of strengthening weak feet and building the plantar arch back up is to pop a towel onto the floor with a small weight at the end of it, and typically scrunch the towel towards you using your toes. This works the muscles on the underside of your feet and can be done under your desk at work, or in front of the telly at home. Doing this every day will really help to restrengthen your feet, and you may be surprised how much it affects little niggles further up your body. It's called the kinetic chain for a reason – everything is connected!
Another really easy way to retrain your feet to postural correctness is by training barefoot as much as possible. This is, after all, how the body was designed to function; not wrapped up in air-cushioned glory. If your gym is funny about people wandering about bare-foot, consider buying some flat soled shoes or foot gloves, which are pretty much like socks but with a 'finger' for each toe, if you see what I mean! These feel odd to begin with, but give you a much more natural contact with the floor.
If in doubt, get checked out!