Occupational
Ergonomics and Biomechanics Laboratory
|
|
|
Sponsor: National Institute for Occupational Safety and Health (R01 OH07793)
|
|
Send mail to
webmaster@engr.wisc.edu with
questions or comments about this web site.
|
This research studies the effects of repetitive eccentric exertions in
industrial power hand tool operation on biomechanical properties of muscle and
tendon in order to better understand the etiology and prevention of work related
musculoskeletal disorders. It is hypothesized that increased power tool reaction
force and build-up time corresponds with greater changes in the dynamic
characteristics of the upper limb. A laboratory-based experiment will define the
short-term relationship between repetitive eccentric exertions (i.e. reaction
force magnitude and build-up time) and upper limb properties (i.e. stiffness,
viscous damping and inertial mass). Subjects will repetitively resist forearm supination against a motor for simulating eccentric exertion levels
representative of pistol grip power hand tool operation. Peak torque levels and
build-up time will be experimentally controlled. Forearm mechanical properties
will be measured before and following a period of work. Mechanical parameters
will be ascertained using a unique apparatus that models the forearm as a single
degree-of-freedom dynamic mechanical system by measuring the angular
displacement of a disturbance to a known mechanical system in free oscillation
when the subject uses maximal effort to oppose its motion. Our preliminary data
reveals that significant stiffness and inertial mass changes are observed when
exercising eccentrically at similar intensity levels. Biochemical measures of
blood creatine kinase (CK), and anatomical measures using T2 changes in an MRI
of the forearms will be compared with biomechanical parameters prior to, and
following repetitive eccentric exertions for a random subset of the subjects.
Subjective discomfort will be assessed using a visual analog scale, and forearm
edema and strength will also be measured. The second experiment will assess
similar upper limb biomechanical properties for industrial workers who regularly
perform repetitive eccentric exertions of varying intensity, build-up time and
repetition rate in selected industrial jobs. Subjects will be recruited from
tool operation jobs on a local automobile assembly line. This research can
ultimately lead to better ergonomic interventions through quantitative power
hand tool design guidelines and work
practices based on understanding the damaging effects of exposure to specific
levels of reaction force, build-up time and repetition, as well as providing new
outcome measures for epidemiological studies.