Abstract
Running shoes, and in particular insoles, are the first interface between runners and running surface. Different insole attenuation properties may vary perception of cushioning and, accordingly, the effect on muscle adaptation. The aim of this study is to find the just noticeable difference between four insole materials, and investigate the parameters of in-vitro measurement of impact testing to predict cushioning comfort. Nineteen (n = 19) male participants were recruited from the sports center at the Technical University of Munich with a mean age of 23.89 (SD = 2.31), weight of 73.52 kg (SD =3.08), and height 178.84 cm (SD =2.81). Four insole samples, one with the highest peak acceleration (EPDM =17.9g), one with the lowest (S.Tk = 8.3g) and the two materials with middle range magnitudes (IP.GL= 11.5g and S.Tn = 12.2g), were selected to use in the subjective measurement. We used the impact testing method to evaluate the in-vitro physical properties of insoles in running shoes. In addition, two parameters of peak acceleration were measured as follows: Jolt α was calculated at a slope of between 5-20 % of inertial impact force and Jolt β was calculated at a slope of between 0-88 Newtons of inertial impact force. Participants performed six pairwise comparison tests with shoes which were equipped with one of the four insoles in a random order. A minimum 6% increase in cushioning properties, notably between 11.5g (S.Tn) and 12.2g (IP.Gl), was discerned through the paired tests. In simpler terms, participants were able to detect a mere 0.7g as the just noticeable difference. In addition, our findings revealed that an increase of Jolt α and Jolt β resulted in a reduction in perception of comfort. There was a negative and significant correlation between Jolt α and perceived cushioning and, similarly, between Jolt β and perceived cushioning r (10) = -0.93, p = 0.00001. No correlation was found between peak acceleration and cushioning comfort (p = 0.1). These discoveries may facilitate a better understanding of how human adaptation can occur with different cushioning.