Effects Of Shoe Midfoot Bending Stiffness On Inner-foot Joints Rom During Heel-toe Running

Abstract

Shoe manufacturers focus on footwear design which might affect the function of the footwear as well as foot motion and joint loading to improve running performance and prevent running injury. The longitudinal bending stiffness is considered to be a key feature in running shoe development. However, the majority of the longitudinal bending stiffness studies focus on the forefoot region, little investigation is carried out for midfoot bending stiffness. It is expected that changes in shoe midfoot bending stiffness would alter the foot motion. PURPOSE: The purpose of this study was to examine whether midfoot bending stiffness affects inner-foot joints ROM on frontal plane, thus providing scienticfic priciples for midfoot structure design of running footwear to enhance foot stability during heel-toe running. METHODS: The midfoot bending stiffness of experimental running shoe conditions were 0.069 Nm/°, 0.091 Nm/° and 0.163 Nm/°. Nineteen male runners with a rearfoot strike pattern, and running at least 10 Km/week, were recruited for this study. Kinematic and ground reaction force data were collected at 3.3 m/s using motion capture system (Vicon T20&T40, 200 Hz) and force platform (AMTI OR6-GT, 1000 Hz) during heel-toe running. A custom-made sock technology and a multi-segmental foot model were used to find the internal movements of foot segment in the shoe. RESULTS: Forefoot to midfoot interaction indicated the frontal plane ROM (p = 0.020, η2 = 0.196) was significantly greater in both the low stiffness (4.7 ± 1.3°) and medium stiffness (4.6 ± 0.9°) shoes compared to the high stiffness shoe (4.2 ± 1.1°) during running stance phase. A significant main effect was seen for the frontal plane ROM (p = 0.005, η2 = 0.258) on the forefoot to rearfoot discrete joint. The amplitude was greater in low stiffness (8.7 ± 2.1°) and medium stiffness (8.4 ± 2.0°) shoes relative to high stiffness shoe (7.8 ± 2.0°) during running stance phase. No difference was found for midfoot to rearfoot frontal plane ROM. CONCLUSIONS: The increased stiffness shoe had a splinting effect on the midfoot and rearfoot by reducing ROM in frontal plane to increase the stability of foot segments movement during running stance phase.