THREE-DIMENSIONAL BIOMECHANICAL ANALYSIS OF THE TRUNK AND UPPER EXTREMITY DURING WHEELCHAIR PROPULSION WITH CONSIDERING THE EFFECT OF MUSCLE FORCES

Abstract

INTRODUCTION -The number of wheelchair users continues to increase, but limited research has been conducted with respect to the kinetics of wheelchair propulsion. In many studies I it is mentioned, most paralyzed patients suffer from shoulder pain. This problem is significantly caused by the forces and moments forcing upon the upper extremity and trunk during wheelchair propulsion. Therefore, establishing an investigation leading to optimal wheelchair/ user match to facilitate effective and safe activity is essential. In this research, our aim is obtaining the forces and moments at the joints of the user during wheelchair propulsion. therefore, by using the concepts of biomechanics and robotics, the trunk and upper extremity are modelled as a 3-D Iinkage system with eight degrees of freedom which representing the trunk, arm, forearm and hand. In this model, the most important muscle forces of the trunk and upper extremity in wheelchair propulsion are forcing on the linkage system[Van der Helm, 1991]. The kinetical analysis of the model has been developed, by using the Newton-Euler equations to give the forces and moments at the joints. In parallel the forces and moments which are present at the hand/rim interface during wheelchair propulsion, is collected via a specific wheelchair instrumented with transducers to record them. For kinematical analysis of the wheelchair user, some markers are attached to the joints. The markers provide the possibility of recording the joints' paths in space via videography using two cameras. The images are translated to a computer by using a video blaster board. The user is informed to propel a specific wheelchair at a predefined velocity. Meanwhile, simultaneous output of the experimental set-up for kinematical analysis, and the applied forces and moments to the users hand, is fed in to a computational programs. This program has been written for kinetical analysis of the model. RESULTS -Having mass center of mass and moments of inertia of the users trunk, arm, forearm and hand, the program which has been written for kinetical analysis, yields to give the forces and moments at the joints vS. time. CONCLUSION -To obtain an optimal wheelchair / user match one can change the geometrical dimensions of the chair such as rim diameter, height and placement of the seat, and also propulsion technique and determine their effects on the forces and moments occuring at the joints. Meanwhile, one can use this method in sport for athletes with disabilities. REFRENCES Van der Helm,F.C.T and veenbaas, R(1991): Modelling the mechanical effect of muscles with large attachment sites: Application to the shoulder mechanism. J.Biomechanics. VoI.24,No.12,PP.1151-1163.