The design, construction and evaluation of sprint footwear to investigate increased sprint shoe bending stiffness on sprint performance and dynamics

• Main Author: Vinet, Andrea M
• Format: Dissertation
• Language: English
• Published: Loughborough University 2014
• Subjects: Additive manufacturing; Footwear; Sprint; Stiffness

Previous work has shown the potential to improve sprinting performance through adaptations to the bending stiffness of sprint shoes. In addition, it has been suggested that the bending stiffness need customising to the individual to achieve maximal performance. However, ambiguous sprint performance results in recent literature with increasing bending stiffness of sprint shoes, in addition to a lack of detailed biomechanical data collected, has lead to considerable uncertainty of the potential to customize the bending stiffness of sprint shoes to individuals for maximal performance. Thus, the aim of this work is to develop functional sprint footwear in a range of different bending stiffnesses in order to explore the effects of increased sprint shoe bending stiffness on sprinting performance and lower limb dynamics. Mechanical test procedures were implemented to both validate the mechanical testing methodologies and benchmark the mechanical properties. A novel mechanical test apparatus and methodology were specifically designed to evaluate the traction properties of sprint shoes. A minimum level of traction generated among commercially available shoes was identified as the minimum level of sufficient traction. The methodology developed by Toon (2008) was used to measure bending stiffness. No trends were detected towards the introduction of stiffer commercially available sprint shoes. A novel construction method using laser sintered (LS) nylon-12 was introduced, producing bespoke sprint shoes sole units in a range if bending stiffnesses with sufficient traction for sprinting. A novel process for assembling the LS sole units with standard uppers was presented, producing durable shoes with a high quality finish. Methodological concerns were addressed in an examination of the effect of commonly used sampling rates (SR), filtering frequencies (fc), and definition of the MPJ on resulting metatarsophalangeal joint (MPJ) kinematics and kinetics in sprinting. MPJ angular range of motion and angular velocity were significantly reduced with changes in SR, fc and MPJ definition, while significant differences in MPJ kinetics with changes of MPJ definition. The influence of shoe stiffness on sprinting performance and step characteristics was assessed using three sprint shoe conditions, up to 7 times stiffer than average commercially available. Results showed a significant increase in sprint time and a significant decrease in ground contact time in the stiffest shoe condition, with all of the participants producing their best sprints in the least stiff shoe condition, indicating the shoe conditions were too stiff. The differences in the trends observed between the group mean and the individual results indicate that both a single subject and group mean analysis be carried out in future research. The influence of shoe stiffness on sprinting performance and the kinematics and kinetics of the MPJ and ankle was assessed separately in the acceleration and maximal speed phases using three sprint shoe conditions, up to 3.5 times stiffer than the average commercially available. Results showed no change in sprinting performance. Increasing the bending stiffness resulted in significant decreases in the amplitude of MPJ and ankle kinematics, in addition to temporal changes in the occurrence of peak values. The effects of increasing the bending stiffness of sprint shoes on the kinematics and kinetics of the lower limb were more pronounced in the acceleration phase compared to the maximal speed phase.