Biomechanical and perceptual cushioning sensitivity based on mechanical running shoe properties

Abstract

Mechanical shoe properties impact running biomechanics, triggering subjective shoe perception. Regarding midsole hardness little is known about the minimal mechanical alteration needed to change running biomechanics and perception. Three ethylene-vinyl acetate midsoles differing in rearfoot hardness (47, 53, 57 Asker C), and peak rearfoot impact acceleration (11.65, 12.40, 12.96 g), were used to create experimental shoe conditions (softer, medium, harder), featuring differing peak rearfoot impact accelerations (12.83, 13.49, 13.95 g) when measured with insoles. Twenty-five male rearfoot runners ran on a concrete loop, while capturing ground reaction forces and lower extremity kinematics of eight valid right foot ground contacts in each shoe. Perception of shoe cushioning and shoe rebound was also assessed during these runs using a 15 cm visual analogue scale. Variable magnitude means were compared for main effects (p < 0.05) by repeated measures analysis of variance, Bonferroni post-hoc tests, and effect size estimation (ηp2). No lower limb kinematic effects were induced by the shoes. Kinetically the softer shoe significantly reduced maximal vertical loading rate 1 compared to the medium and harder shoe (131.28 to 138.40 and 139.54 bw/s). Runners significantly perceived the difference in shoe cushioning between the softer and harder shoe (6.32 to 8.06 cm). For the running shoe model in this research a difference in mechanical peak impact acceleration of 0.66 g was sufficient to elicit different biomechanical loading. To elicit different cushioning perception a mechanical difference of 1.12 g was sufficient, resulting in a maximal vertical loading rate 1 difference of 8.26 bw/s. Knowing a shoe model’s biomechanical and perceptual sensitivity to mechanical alteration allows better informed design, development, and manufacturing decisions.