BIOMECHANICS OF WHEELCHAIR RACING

Abstract

An additional assistive device - such as a wheelchair or a prosthesis often forms an integral part of the disabled athlete and a functional prerequisite for mobility and sports participation. The use of such a tool in high performance sports situations sets typical demands to the performance capacity of the athlete. but also to the methods end techniques of biomechanical research. Apart from environmental f a e m research into the optimization of performance in wheelchair racing will have to focus on three areas of interest Firstly, the dynamics and design of wheelchairs should conform to the laws of (vehicle) mechanics. Rolling resistance, air drag and internal friction must be minimized, since these forces determine the e x m a 1 power output which the human engine will have to deliver at a certain speed. 'Lightweight' and 'high tech' an the keywords of contemporary racing wheelchairs. Their design is task-directed and - within this framework - tuned to the individual demands of the athlete. Secondly. work capacity and propulsion technique an major determinants in the performance of the human engine. Performance is primarily dependent upon the functional and training status of the upper body of the athlete. Understanding the detailed functional role of the upper body in wheelchair track performance requires a combined biomechanical and physiological study of arm work under realistic experimental conditions and in different groups of subjects. Thirdly, performance of the wheelchair-user combination is influenced by the interfacing between the wheelchair and the athlete. Development of fitting criteria with respect to geometry and mechanics of the wheelchair requires a combined biomechanical and physiological approach too. Wheelchair propulsion is frequently studied on a motor driven treadmill. 'Three-dimensional kinematics and electromyography arc combined in conjunction with overall physiology and prove to lead to a valuable description of same biomechanical aspects of wheeled mobility. To enable a more detailed biodynamic analysis of wheelchair propulsion a computer-controlled wheelchair ergo meter was designed. Through simulation of wheelchair propulsion force characteristics in all interfacing units of the wheelchair-user combination an studied: the seat. backrest and the rims. Thus torque production. efficacy of force generation and the net torque and power production over the different joints are studied under (sub-)maximal performance conditions and in conjunction with different aspects of the wheelchair-user interface. Within this framework special attention is dedicated to the functional anatomy and biomechanics of the shoulder mechanism, which is crucial in power production. Modelling of the shoulder mechanism - based on detailed dissection studies - will help clarify its role in propulsion technique and will help specify wheelchair fitting guidelines. This integrated anatomical. biomechanical and physiological approach may eventually help explain the human potential and limitations in arm work and the mechanisms which lead to overuse injuries in the arm-shoulder complex.