Limitations of functionally determined joint centres for analysis of athletic human movement: a case study of the upper limb

Much research is ongoing into improving the accuracy of functional algorithms to determine joint centres (JC), but there has been limited testing using human movement data. This paper is in three parts: Part 1, errors in determining JCs from real human movement data using the SCoRE method; Part 2, variability of marker combinations during a punch; Part 3, variability in the JC due to reconstruction. Results indicate determining the JC of the shoulder or elbow with a triad of markers per segment with an accuracy greater than 20 mm is unlikely. Part 2 suggests conducting a pilot study with abundant markers to obtain triads which are most stable due to differences of 300 to 400% in variability between triads. Variability due to the choice of reference frame for reconstruction during the punch ranged from 2.5 to 13.8 mm for the shoulder and 1.5 to 21.1 mm for the elbow. It would appear pertinent to enhance the practical methods in situ than to further improve theoretical accuracy of functional methods

A methodology to investigate the relationship between lower-limb dynamics and shoe stiffness using custom-built footwear

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 selectivelaser- 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 9N, 24.5 N, and 38N in flexion and 7.4 N, 14.7 N, and 26.1N in extension. The participant performed best in the medium-stiffness shoe for squat jumps and the maximumstiffness 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