Improvement of safety shoe fit - evaluation of dynamic foot structure

Abstract

Safety shoe development is based on static foot measures, which are transferred to last design. However, workplaces are not just static (‘standing workplaces only’). The aim of the present study is to examine static and dynamic foot loading of workers to determine whether foot morphology changes between different loading situations. The results could be used to improve last and shoe design to improve the fit of safety shoes. 1024 workers at different industrial locations in Germany took part in the study. The DynaScan4D dynamic scanner system was used to measure static and dynamic foot morphology during different phases of ground contact. All scan variables were selected based on measures required in the last development process. Cohen’s d (effect size) was calculated to identify individual differences between maximum values during the stance phase of walking and static values in standing. Stepwise multiple linear regression analysis was performed to identify possible influencing variables with regard to differences between static and dynamic values. Several foot measures showed relevant differences between dynamic and static loading. Interestingly, most length, width, height, and angular measures increased during dynamic loading (compared to static loading), whereas all circumference measures decreased. None of the tested variables (age, BMI, gender) predicted the differences between the two loading situations. Most dynamic changes are practical relevant changes between static and dynamic loading. Regarding the fit of safety shoes, it seems appropriate to adapt these changes to the last or shoe design.