Effect of increased shoe longitudinal bending stiffness on ankle and foot biomechanics in jump-cut movements of low and high degrees

Lateral ankle sprains are the most common injuries in indoor and court sports, with ankle inversion being a primary injury driver. Stabilising the ankle during multidirectional changes is crucial for injury prevention. Conversely, increased shoe stiffness has been hypothesised to influence the magnitude of ankle inversion and may raise the risk for ankle injuries. Therefore, the purpose of this study was to investigate the influence of shoe longitudinal bending stiffness on ankle biomechanics during indoor and court sport-specific cutting movements. Biomechanical data from 19 participants were collected using a motion capture system and force plate. A jump-cut protocol with two different cutting directions after landing was performed in indoor shoes with and without carbon plate inserts of varying stiffness. Ankle kinematics and kinetics were analysed with statistical parametric mapping and repeated measures analysis of variance. A significant increase in ankle inversion during the 180 degrees cut and a reduction in forefoot inversion (foot torsion) for stiffer footwear conditions during both the 45 degrees and 180 degrees cut were observed. While dorsiflexion moments differed during the last 10% of ground contact, ankle inversion moments did not significantly diverge between shoe conditions. Furthermore, a noteworthy correlation between footwear longitudinal bending stiffness and torsional stiffness was identified. In conclusion, increased bending stiffness significantly affected ankle and foot kinematics. The ankle compensated for restricted mobility and higher demands during high-degree jump-cuts, while foot torsion played a more prominent role in low-degree cuts. The heightened ankle inversion during high-degree cuts may induce an elevated risk for lateral ankle sprains. Further longitudinal studies are necessary to comprehensively understand injury incidence and the role of shoe stiffness in injury prevention.