Minimize any running shoe

Recently, Fellrnr pared away the midsoles from a pair of Nike Free to enhance their minimalism (http://fellrnr.com/wiki/Modified_Nike_Free). He opined that the Nike Free's absent outsole makes it more suitable for this modification than conventional shoes. Because such modification will be more useful if it works all shoes, we propose an alternative method that circumvents the outsole reattachment problem foreseen by Fellrnr. The shoe model used in this experiment is the Asics Patriot 4, US size8.5 - this is a low end model without gel pads.

The modification entails drilling a series of holes into the midsole from the side. The holes run across the width of the midsole to exit on the opposite side. The midsole thickness determines the right drill size. For the aforementioned shoe model & size, either 6 & 8 mm drill sizes are suitable. A larger drill size has the advantage of removing more material, however, it is accompanied by a higher risk of rupturing the midsole (rupturing 'inside' the shoe is not a problem as it is hidden by the insole). The number of holes and the spacing between them allow the shoe stiffness to be manipulated. For this experiment, we used three and five holes under the heel and the ball, respectively.

The modified shoe feels decidedly softer and more flexible.