M.Sc Thesis

M.Sc StudentRoth Navit
SubjectMechanical Impedance of the Loaded Human Arm in Walking
DepartmentDepartment of Biomedical Engineering
Supervisor PROFESSOR EMERITUS Joseph Mizrahi


In daily activity our upper limb is subjected to indirect perturbations. An interesting question is how our body controls joint movements in order to perform given tasks. The goals of this research were to study: (a) upper limb reaction to perturbations while walking; (b) influence of short term motor learning on the mechanical impedances; (c) by successive immobilization of each joint, investigate the role of each joint in the mechanical impedance of the upper limb (d) study activation of the major muscle groups of the elbow joint while walking. To achieve these goals 4 female subjects walked on a treadmill while holding a filled cup with liquid, taking care to retain the liquid within the cup. The following measurements were made: angles of shoulder, elbow and wrist joints, knee impact, E.M.G from biceps and triceps and liquid level. The experiments where carried out in two conditions: no joint constraint, and with immobilization of each of the wrist, elbow and shoulder joints.

The model results indicate that the wrist joint is characterized by stiffness and damping whereas the elbow and shoulder joints are characterized by stiffness, including a constant element and an angular-velocity-dependent element. The results also showed that elbow limitation has the greatest effect on deviation from the target function and that following immobilization of joints, the most pronounced changes in the results where in the distal joints.

This research provides means for better understanding of impedance control of upper-limb joints. Future research should focus on applying this model to subjects with joint limitations and on further investigation of the motor learning effects.