Date of Award

Spring 2009

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Biomedical Engineering

First Advisor

Winters, Jack

Second Advisor

Myklebust, Joel

Third Advisor

Beardsley, Scott


The upper extremity (UE), including the shoulder complex, , provides the ability to generate forces in multiple directions within the arm workspace. The inherent complexity and high functionality make the analysis of arm movements and tasks challenging. This takes on special significance when trying to understand how arm dysfunction relates to accessibility when performing manual operations within the local environment. This project implements a pilot study aimed at evaluating shoulder-arm-torso EMGs and manually applied forces in young healthy, aged healthy and stroke affected population in different regions of a 30 arm workspace. The results supported the general hypothesis that muscle activations are dependent on force direction and hand position, and differences in these parameters are affected by age and disability. The results show that the direction in which a certain force is applied influences the performance of the individuals. This inability to apply forces in the more 'difficult' Up and Right directions is prominent in the stroke population. The finding in all three groups that forces in undesired directions accompany the direction specific force application tasks often with statistically significant trends, suggests that off axes forces are often involuntary and normal. The prominence of such forces in the disabled group supports the force producing abnormalities due to functional arm impairment. The EMGs indicate variations as per regions of the workspace and are force direction-dependent for the young and aged population. The lower variation in the older adults EMGs compared to the young suggests age-related muscle weakness, poor grip control and postural instability. The stroke subjects' EMGs showed lower variability in some regions of workspace, and inspection of videos showed considerable active trunk movement, unlike for normals. It is inferred that stroke limits the ability to vary the recruitment of key muscles for force application tasks, and thus the degree of access within the workspace, and that this is evidently compensated for in part by mechanisms like recruitment of additional degrees of freedom (i.e. trunk movement) and recruitment of additional muscles.



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