This is a bit of a plea to not do away with the medial posting in the dual density midsoles that used to be so popular to deal with ‘overpronation’. There is a trend away from them. That is a shame and unfortunate. I have my reasons as to why we still need to use them when we need to use them.
The medial posting feature was introduced as part of a suite of “motion control” feature in the 1980’s to help deal with the alleged problems of ‘overpronation’ of the foot. It was never going to stop it as it simply ignored what the more common reasons of what was ‘overpronation’. It may have helped the running shoes longevity by not allowing the midsole to bottom out so quickly in those who do ‘overpronate’. This is also assuming that we actually want to do something about ‘overpronation’ and that it is a cause of so many problems that it is alleged that it is (that’s a discussion for another time). As a result of these issues, there is a trend away from the use of medial posting.
Having said that, I do like the medial posting as a design feature and still want to be able to use it as they do have a specific effect that I like to be able to use. Medial posting does have the affect of moving the center of the ground reaction forces more medial. That medial movement of the center creates a larger lever arm from that center of pressure to the subtalar joint axis. Being able to do that is really important in those with a more medial located subtalar joint axis. I certainly get those runners who have a more medial subtalar joint axis into a shoe with the medial posting in the midsole, as it really is helpful. The problem is the number of shoes that have this medial posting is dropping. That is a shame.