• shoe cushioning
• trail running
• running biomechanics
• impact test
• footwear perception

Trail running has recently become a very popular sport activity. Its practise takes place in natural environments like forests and mountains. The spreading popularity is leading the footwear industry and R&D to create new specific innovative technologies. This work is part of a long-term project that aims to develop a new cushioning solution. “Cushioning” refers to the capacity of the shoe to absorb the force of an impact. The optimal trail running footwear sole must be chosen according to the weight of the trainee, the cadence and type of usual gait, the temperature of the environment, and the type of training surface. In this context, the request for a variable-on-demand cushioning may represent the solution. The first step has been to develop a mechanical characterization setup able to quantify the level of cushioning and to study a set of commercially available shoes and their effect on running biomechanics and users' perception. Seven runners took part in indoor and outdoor sessions, testing and rating eight different pairs of shoes. The mechanical impact test allowed us to identify a virtual parameter and its range of values to identify the perceived level of cushioning. Two accelerometers were attached to the metatarsus and the tibia. The median frequency extracted from the first 25 % of the stance phase of the signal was found to decrease with the higher perceived level of cushioning, becoming the best candidate to biomechanically describe this footwear property.