The limited customisation in commercially available wheelchairs does not always appropriately accommodate the anthropometric variations resulting from specific impairment. Wheelchair racing athletes demonstrate up to 3.8% total body mass greater in the upper extremities, and up 9.8% total body mass reductions in their lower extremities, and between-limb asymmetries of 62.4%. As a consequence, athletes may not have the stable base of support required for optimal propulsion. The optimisation of an entire wheelchair to match unique athlete geometry is both time consuming and costly, as wheelchairs cost over $2000 each. The use of assistive technology can provide an efficient transition between the commercially available equipment and the unique athlete anthropometry. Customised seating interfaces offer a time and cost effective solution, facilitating regular modifications to satisfy athlete growth. These solutions have been used extensively in clinical applications for enhanced stress distribution and injury prevention at the seating interface; however, they have not yet been applied to sporting contexts. The goal of this research was to investigate the performance impact of customised seating interfaces on wheelchair racing propulsion technique. Supplementary goals included the development of practically viable instrumentation solutions and a musculoskeletal model representative of the unique wheelchair racing athlete anthropometries and physical capabilities to assess injury risk to analyse performance impact holistically. The research was split into four main themes: 1. Verification of the importance of the seating interface relative to other key performance parameters such as aerodynamics and glove selection. 2. Instrumentation of the hand-pushrim and seating interfaces 3. Development of a musculoskeletal model 4. Computational modelling of performance and injury risk Computational modelling was performed in the OpenSim environment which coupled kinematic inputs from 3D motion capture (VICON Bonita V16; Oxford Metrics, Oxford, United Kingdom), with kinetic inputs from a pressure mat at the seating interface (XSensor LX100; Calgary, Alberta, Canada) and inertial measurement units (IMUs) (I Measure U; New Zealand) to estimate the hand-interface interactions. This was achieved using Newton’s Second Law, incorporating athlete-specific mass data (from the analysis DXA scans), and acceleration measured from the IMU. Customised seating interfaces reduced the undesirable peak translations of the knee by up to 41.8% and lateral translation of the spine by 33.4%. These translated towards enhanced performance, with an average performance time reduction of 29.8 s (3.7% race time) in the eight international competitions following the inclusion of the customised seating interface. Additionally, athletes using cushioned seating interfaces had reduced peak pressures at the seating interface as compared to those without the interface. Instrumentation can be used outside the laboratory environments, and can, therefore, be applied in the daily training environment to optimise performance preparation. This research provided foundation work for the use of computational biomechanical analyses for the holistic assessment of wheelchair racing performance. Whilst this research has demonstrated the potential impact computational modelling approaches can have on the performance preparation of athletes, some areas for further refinement have been identified. Future research into the processing of IMU data and the validation of musculoskeletal models for wheelchair racing athletes are the critical areas for improvement. Once achieved, the computational modelling approaches explored in this research can positively impact performance outcome, particularly when coupled with the optimisation of equipment, such as customised seating interfaces.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 201
