Kathleen Shyhalla, PhD

Experimental Work

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expsetup Repetitive industrial work with precision requirements
had been associated with the development of upper extremity musculoskeletal disorders.
To learn more, experiments
were conducted in the laboratory.
During experiments
People performed 4 repetitive tasks.

The probe's trajectory
People's joint angles
Electromyographic (EMG) activation patterns
from 6 shoulder muscles

Were monitored continuously.
Main Tasks lasted 7 minutes.
People repetitively moved the probe between the Home (left) and target (right).
Tasks were 4 levels of accuracy.
Accuracy was increased by decreasing target size. 
During composite tasks,
 people repetitively moved the probe
between the Home and a ray of 6 targets for 45 seconds. 
Composite tasks and discomfort surveys
preceded and followed each Main Task.



Velocity profile of probe during high precision (left) and low precision (right) tasks


Velocity profile of forearm during tasks


Anterior deltoid EMG during tasks