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My research objectives are to understand the mechanisms that influence the
performance of skeletal muscle and gross human movement, and to develop
tools based on this information that can be used to assist people afflicted
with various musculoskeletal disorders, to maximize athletic performance,
and to minimize worker fatigue. I pursue two basic areas of research.
The first area involves the study of fundamental properties of biological
tissues (i.e. bone, ligament, tendon, and muscle). The second area involves
the study of gross limb dynamics and how the properties of individual
muscle-tendon units contribute to these dynamics. I believe that simultaneous
investigations of these two research areas are essential for understanding
the mechanisms contributing to human movement and performance. I utilize
both animal and human models in my experimental investigations. I also
utilize computer modeling and simulation techniques to study the interactions
of various factors affecting muscle and human performance. Click here
to view a flyer describing Musculoskeletal Biomechanics
Research conducted within the Human Performance Laboratory at the
University of California - Davis.
Summary of Selected Research Projects:
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Isolated muscle-tendon testing is conducted to determine
a) the interaction between stretch-shortening cycle kinematics and
muscle force potentiation, b) the effects of muscle connective tissue
on muscle energy storage and reutilization, and c) the affects that
different muscle-tendon lengthening procedures, used to treat joint
contracture, have on muscle-tendon performance. Shown here is a muscle-
tendon lengthening procedure performed on a rat. The mechanical properties
of the lengthened muscle-tendon units were determined three weeks
post surgery and recovery. |
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Musculoskeletal modeling and computer simulation techniques are
used to study the complex interactions that exist between anatomy
and human movement performance. Shown here is a digital geometric
model of the right leg. Computational techniques have been developed
to allow atrophy and hypertrophy to be simulated in individual muscles.
The output from this model is utilized in computer simulations of
lower limb dynamics to study the affects the muscle volume changes
have on limb inertial properties and limb dynamics.
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Musculoskeletal modeling and computer simulation techniques can
also be used to evaluate man-machine interfaces and identify implement
designs or human movement strategies that will facilitate a given
movement task. Shown here is a pediatric wheelchair being tested
to determine the forces that a child must apply to the hand rim
or tire in order to propel the wheelchair in their home or school
(e.g. floor transitions, ramps, thresholds). Experimental data are
combined with musculoskeletal modeling and computer simulations
of wheelchair propulsion. The objective of this project is to design
a computer program that will prescribe optimal wheelchair setup
to allow small children to self propel their wheelchairs.
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Sports equipment (i.e. bicycles, oars, boats etc.) can be designed
to maximize the power producing potential of the human body. This
requires knowledge of the relationships between human performance
and limb kinematics, kinetics, and the loads imposed on the body
by external forces. One study involves finite element modeling of
an oar blade and subsequent design modification to enhance the rower's
performance. The blade design is customized to provide fluid drag
characteristics that match optimal movement kinematics and kinetics
for a rower.
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Shown here is a customized dryland rowing ergometer developed to
provide kinematic and kinetic feedback to a rower as he/she rows.
Hip, knee, and elbow kinematics are presented to the rower or coach
along with the instantaneous pulling force and power produced. The
feedback information can be used to correct technique and identify
rowers with similar power production profiles. This is one of the
most comprehensive real-time feedback systems in the world.
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Shown here are two ultrasound images of the gastrocnemius muscle,
one of the muscles on the back of the lower leg. Ultrasound is being
used to non-invasively study the behavior of muscle and tendon as
they act within the body under various conditions. The top image
is from a relaxed muscle and the bottom image is from a contracted
muscle. The two images illustrate how the orientation of the fascicles
within the muscle change with muscle activation.
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Lateral force transmission between adjacent muscles is being studied
to better understand how this mechanism of force transmission may
affect the functional outcome of various surgical procedures such as
tendon transfers and the use of tendon donors for ligament grafts. Two adjacent
muscles of the chicken leg are shown here being tested for passive lateral
force transmission.
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Injury prevention is also an area of research interest. Shown here
is an experiment designed to simulate a half day of down-hill skiing.
Throughout the experiment kinematic and joint strength data were
recorded. The ideas being tested were that throughout a ski session,
muscle fatigue develops which causes a skier to alter his/her body
position and reduce their neuromuscular response times. Such changes
could place the knee at risk for injury. An understanding of the
factors that may lead to injury is necessary to develop strategies
to prevent injury.
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