Why do arch supports hurt my feet?
Arch supports probably don’t hurt your feet.
Size and width explain much of what makes shoes comfortable and also explain much of what makes shoes painful. Pain, even in the arch, is most likely due to too little room, not to arch supports.
A foot has three arches
Biomechanists sometimes describe the foot as having three arches. Looking down at one foot: there is a longitudinal arch on the medial side, a longitudinal arch on the lateral side, and a latitudinal arch beneath the instep. This post will be referring to the first of those three arches because a shoe’s arch supports are usually for that arch.
Joints connect to each other the bones that form the arch. Those joints allow the bones to change positions. Which is what the bones do when you walk and run. Ground reaction forces can easily reach three times bodyweight. Those big forces will move bones into positions that allow your foot to function well when walking and running.
When it comes to the placement of bones during locomotion, ‘normal’ varies among individuals. The bones in one person’s foot may move to some set of positions, whereas the bones in a different person’s foot may move to a different set of positions. Let’s call the position of the bones, in combination with the pattern of muscular activation in the lower leg, the preferred movement path.
Sometimes the problem isn’t arch supports but the wrong size
The foot will need an adequate amount of room for its bones to move into their preferred positions. If a shoe is too small—if a size 9.5 foot is squeezed into a size 8 shoe, for example—there may not be enough room for those bones. There may be an ever-so-slight disruption to the preferred movement path. That disruption would be repeated with every step. During the hundreds, if not many thousands, of steps during just one workout, those disruptions could create discomfort in the arch or in other places. It may be assumed that the pain is caused by the arch supports. But the more likely cause is the size.
There is a similar problem with width. If an EE width foot is squeezed into a D width shoe, for example, there may be too much force against the longitudinal arch. In that event, the foot will protrude over the midsole. The portion not supported by the midsole will be suspended in the air by the shoe’s upper. As the arch of the foot is squeezed against the upper, the upper pushes back against the arch. That force against the arch could cause pain. In this case, again, the more likely cause of the pain is the width, not arch supports.
The best shoe is the comfortable new shoe that fits. Find a running shoe store that focuses on comfort, and that will measure both of your feet.