BIOMECHANICS OF WHEELCHAIR RACING

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

NEW METHODS FOR MOBILITY PERFORMANCE MEASUREMENT IN WHEELCHAIR BASKETBALL

Increased professionalism in wheelchair sports demand a more precise and quantitative measure of individual wheelchair mobility performance, to allow it to be an evaluation measure of wheelchair setting or training optimization. This research describes the application of an inertial sensor based method for measuring wheelchair kinematics and a factor analysis based selection of outcomes best describing wheelchair mobility performance. This set of kinematic outcomes was analysed for sensitivity towards wheelchair performance differences due to competition level and classification of the match data of 29 wheelchair basketball athletes. The method proved sensitive and is believed to provide a solid basis for a kinematics based definition of wheelchair mobility performance in sports

Task variation during simulated, repetitive, lowintensity work – influence on manifestation of shoulder muscle fatigue, perceived discomfort and upper-body postures

Work-related musculoskeletal disorders are increasing due to industrialisation of work processes. Task variation has been suggested as potential intervention. The objectives of this study were to investigate, first, the influence of task variation on electromyographic (EMG) manifestations of shoulder muscle fatigue and discomfort; second, noticeable postural shoulder changes over time; third, if the association between task variation and EMG might be biased by postural changes. Outcome parameters were recorded using multichannel EMG, Optotrak and the Borg scale. Fourteen participants performed a one-hour repetitive Pegboard task in one continuous and two interrupted conditions with rest and a pick-and-place task, respectively. Manifestations of shoulder muscle fatigue and discomfort feelings were observed throughout the conditions but these were not significantly influenced by task variation. After correction for joint angles, the relation between task variation and EMG was significantly biased but significant effects of task variation remained absent.Practitioner SummaryComparing a one-hour continuous, repetitive Pegboard task with two interrupted conditions revealed no significant influences of task variation. We did observe that the relation between task variation and EMG was biased by posture and therefore advise taking account for posture when investigating manifestations of muscle fatigue in assembly tasks