It has been demonstrated that, by varying the mechanical properties of footwear, the sprinting performance can be improved. It has been hypothesized that, for maximal performance, tuning the shoe stiffness to the requirements of the athlete is necessary. The aim of this study was to investigate the feasibility of using sprint shoes constructed with selective-laser-sintered Nylon 12 sole units for sprint-related jump tasks and to examine whether adaptations to the mechanical properties of the footwear were sufficient to elicit changes to lower-limb dynamics during athletic performance. An internationally competitive sprinter completed sprint-related jump metrics in various selective-laser-sintered shoes with bending stiffnesses of 9 N, 24.5 N, and 38 N in flexion and 7.4 N, 14.7 N, and 26.1 N in extension. The participant performed best in the medium-stiffness shoe for squat jumps and the maximum-stiffness shoe for bounce drop jumps. This investigation has demonstrated that selective laser sintering can produce high-integrity footwear with markedly different mechanical properties. Such footwear, coupled with an appropriate test method, has been shown to be suitable for investigating the relationship between lower-limb dynamics and shoe stiffness.

The primary kinematic factors relating to sprinting performance may be influenced by the mechanical properties of the footwear worn. It was hypothesized that, compared with the barefoot condition, sprint spikes would influence sole angle to the ground, and metatarsophalangeal joint (MPJ) extension and flexion. High-speed video recording was used to analyse key kinematic variables of the foot segments and the MPJ in barefoot and shod running conditions. The stance phases of four sprinters (two male) were captured in the blocks, at 10 m and at 50 m into a maximal effort sprint. Angular range and angular velocity during MPJ flexion at 10 m and 50 m were reduced significantly when wearing sprint spikes. The mean angular range at 10 m was reduced by 11°, 13°, and 5° for the initial flexion phase, the extension phase, and the final phase of flexion respectively. This effect was larger during ground contact at 10 m versus 50 m. Sole angle to the ground at take-off was lower in the sprint spike shod condition than in the barefoot condition. Performance-related parameters such as degree of MPJ extension, MPJ extension velocity, and sole angle to the ground are influenced by sprint spikes when compared with the barefoot condition.

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