The study shoes are prototypes and will be anonymized for the purpose of this trial. The sole of the shoes will be customized so that the two running shoe prototypes will be exactly the same (same midsole, same outsole, same upper), except for their cushioning properties which will differ by more than 35%, while remaining within the range of the shoes available on the market. The difference in cushioning properties between the shoe versions will be created by modifying the midsole material, i.e. chemistry, density and therefore the hardness of the Ethylene Vinyl Acetate (EVA) foam. In order to provide accurate data on the technical specifications (i.e. stiffness ) of each shoe model, a set of 40 shoes (10 pairs per condition) will be tested for cushioning properties by the manufacturer according to a standardized protocol (Impact test: ASTM1614, Procedure A).