Clark Dickerson

Dickerson, Clark

Clark Dickerson

Assistant Professor
BSc (Alfred), MSc (Clemson), PhD (Michigan)

Contact:

Office: BMH 3034
Telephone: 519-888-4567, ext. 37844
e-mail: cdickers@uwaterloo.ca
FAX: 519-746-6776

Research:

Work related musculoskeletal disorders (WMSDs) are pathologies that are the result of exposures to stressors in work environments, and represent over $100 billion in annual societal costs. Commonly injured areas of the body include the low back, the wrists, and the shoulder. My research focuses on identifying, quantifying, and reducing work-related stresses in the shoulder through mathematical modeling and experimentation.

Work tasks include dynamic movements that have force and precision requirements. In order to quantify the impact of work tasks on the shoulder, several biomechanical computer models are being developed and experimentally evaluated. First, an external dynamic model of the upper limb is used general joint torques and forces. A second model of the internal shoulder geometry establishes the line-of-actions of each of the muscles, as well as the positions and orientations of each bone. This model calculates the instantaneous orientation of thirty-eight muscle units while respecting orthopedic obstacles using geodesic conventions. A third model distributes the forces and torques created by the external loads amongst the muscles using an optimization approach in order to estimate specific tissue stresses. A fourth model describes a mathematical formulation of physical effort perception. In the laboratory, experiments are conducted; during which movement, muscle activity, work perception, and hand forces are monitored. The outputs of the models are then compared with collected empirical data.

The primary purpose of this approach is to enable informed prospective job design. Integration of the models with existing software allows simulated jobs to be analyzed for potentially injurious stresses to shoulder tissues in digital design environments, using technologies such as digital human modeling (DHM). Secondarily, increased worker comfort and decreased effort can be achieved in designs through implementation of force-perception relationships that are unique to the shoulder.

This research results in the creation of computerized design tools and biomechanical insights. These can then be used together to improve the safety and usability of workspaces and other man-machine interfaces, thereby reducing the frequency and severity of occupational shoulder injuries.

Three views of an analyzed task: A) Experimental, B) Biomechanical Model, C) Digital Human Modeling Software

Key Publications:

1. Dickerson C.R., Martin B.J., and Chaffin D.B., 2006, The relationship between shoulder torques and the perception of muscular effort in load transfer tasks. Ergonomics, 49(11):1036-1051.

2. Dickerson C.R., Martin B.J., and Chaffin D.B., 2007, Predictors of perceived effort in the shoulder during load transfer tasks, Ergonomics, 50(7):1004-16.

3. *Gatti C., Dickerson C.R., Chadwick E.K., Mell A.G., and Hughes R.E., 2007, Comparison of model-predicted and measured moment arms for the rotator cuff muscles, Clinical Biomechanics, 22:639-644.

4. Dickerson C.R., Chaffin D.B., and Hughes R.E., 2007, A mathematical musculoskeletal shoulder model for proactive ergonomic analysis, Computer Methods in Biomechanics and Biomedical Engineering, 10(6):389-400.

5. Dickerson C.R., Hotchkiss C.E., and Saha, S., 2007, Relationships between densitometric and morphological parameters as measured by peripheral computed tomography (pQCT) and the compressive behavior of lumbar vertebral bodies from macaques (macaca fascicularis), Spine, in press.

6. *Brookham R.L., *Moreton J.N., and Dickerson C.R., 2007, Perception of shoulder muscular effort during low-demand load transfer tasks, Work, in press.

Courses Taught:

KIN 10 Ergonomics Option Seminar
KIN 420 Occupational Biomechanics
KIN 428 Upper Extremity Disorders
KIN 494 Integrative Ergonomics Practicum
KIN 670E Seminar 1:Biomechanics and Ergonomics