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Influence of footwear comfort on the variability of running kinematics†

Footwear comfort is an important factor in design, purchase and use of running shoes but current measures require multiple subjective assessments. Therefore, an objective and more reliable surrogate measure of footwear comfort would be of high relevance. In other research fields, perceived comfort was found to influence the variability of movement execution. Consequently, the purpose of this study was to investigate the influence of perceived footwear comfort on the variability of running kinematics as a potential surrogate measure of comfort. Thirty-six recreational athletes ran in five different running shoes on an indoor track while their running kinematics were recorded using a foot-mounted tri-axial inertial measurement unit (IMU). Footwear comfort was measured through multiple subjective assessments. The relative variability of IMU data was determined across the swing phase of 45 gait cycles and compared between the most and least comfortable shoes. Lower footwear comfort was associated with lower kinematic variability especially in the second half of the swing phase but only for variables that are not directly linked to the forward propulsion during running and mainly describe frontal and transverse joint rotations. The constraints of an uncomfortable shoe may lead to the adaptation of a more monotonous running style with the goal to stay in the least uncomfortable movement path. This finding may partially explain a previously described higher injury risk when exercising in footwear of lower comfort, as more repetitive forces could increase the risk of overuse injury. The results of this study implicate the possible use of IMU-based kinematic variability as a surrogate measure of footwear comfort, which could complement subjective measures.