Defense Date


Document Type


Degree Name

Master of Science


Biomedical Engineering

First Advisor

Dr. Paul A. Wetzel, Ph.D.

Second Advisor

Dr. Mark S. Baron, M.D.

Third Advisor

Dr. Ding-Yu Fei, Ph.D.


Parkinsonian rigidity is caused by the inability of the muscles to relax and extend properly, due to reduced dopamine levels and often begins on one side of the body before spreading contralaterally. The current standard for determining joint rigidity in a clinical setting is a test completed by the clinician based on the feel of the relaxed wrist and elbow joints as they are passively flexed and extended and a series of ordinal rating scales, the Movement Disorder Society’s – Unified Parkinson’s Disease Rating Scale (MDS-UPDRS), Hoehn and Yahr Scale (H&Y), and Parkinson’s Disease Questionnaire-39 (PDQ-39). These methods are used to determine the severity of the patient’s disease and the impact it has on their quality of life, but they lack objectivity and do not differentiate between individual symptoms. We present a torque-based device to objectively quantify rigidity in a PD patient’s arm. The device employs a servo motor-shaft assembly, connected to a rigid forearm sling, and controlled by a computer to passively flex and extend the elbow joint laterally. Two individuals were used for preliminary results in lieu of the patient restrictions due to COVID-19. A sine, ramp, and random (sine-like) stimuli were used on each person during a relaxed phase, and a co-contracted or clenched-fist phase. A torque transducer and potentiometer measured the torque and position with respect to time while angle of rotation, acceleration, and velocity of the shaft were monitored simultaneously to ensure safety. Results showed that the magnitude of rigidity was greater during co-contraction than during relaxation indicating that rigidity can be objectively measured using this device. Quantifying joint rigidity will allow for a better understanding of the mechanisms of rigidity in Parkinson’s and other movement disorders.


© Georgina O. Miller

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