Biomechanical model for the determination of forces on upper-extremity members during standard wheelchair propulsion

New technologies and new configurations have brought great improvements to wheelchair development. These developments create problems for wheelchair users concerned with the choice of the best wheelchair for their specific needs, skills and capabilities. Handicapped people, who exclusively depend on the manual wheelchair for locomotion, face great difficulties because they have constant pain in their upper-extremity members, mainly in the shoulder, elbow and wrist. Manual propulsion can be considered a cyclical effort, thus the pains are symptoms of injuries from repetitive efforts. The problem becomes worse when the user has to overcome architectural obstacles, because it significantly increases the required propulsion force. The aim of this paper is to determine the dynamical efforts over the upper-extremity members during the manual wheelchair propulsion using Newton–Euler and Jourdain equations, and inverse dynamic techniques. The dynamical efforts consider the forces and moments over upper-extremity joints during the propulsion movement. As a result, it is possible to establish a system of equations and thus evaluate the efforts over the joints. Another result is the possibility to simulate the system using the anthropometric values of real subjects aiming at making it easier to choose the best wheelchair, considering his/her physical and anthropometric characteristics. Besides, the study of the propulsion patterns (different patterns of propulsion lead to different biomechanics) allows physical training aimed at improving the propulsion efficiency.