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Whole organ pressure-flow relationship in the rat gracilis muscle
890
Abstracts
ACCELERATIONS
OF
HUMAN
LOWER-EXTREMITY JOINTS THEORETICAL CONSIDERATIONS
INDUCED
BY
MUSCLE
FORCES:
Felix E. Zajac, Michael E. Gordon, Melissa G. Hoy, J. Peter Loan Rehabilitation In biomechanical
Research & Development Center (153). Veterans Administration Medical Center, Palo Ano, CA 94304 and Mechanical Englneerfng Department, Stanford University, Slanford. CA 94305-3030 studies of movement.
of how forces in those excited Planar motion body SegmenlS,
muscles
EMG signals recorded
from muscles
act to move the body-segments,
are often interpreted
or joints.
to find the accelerations
of the joints induced by forces in muscles.
on anthropometry
spanned
in the same direction as the applied muscle torque, bul that the unspanned
unspanned accelerate
joints in either
We found that a uniatticular
on the joint angles. direction.
In contrast
joints in directions
Biarticular
and to “extend”
muscles,
to uniarticular
opposite
however,
muscle torques.
However,
accelerations
depend,
of
the direction
muscles,
act lo accelerate
a biarlicular
muscle
For example,
in
the joint
joints will tend to be accelerated
like uniarticular
may act simultaneously
the knee.
These
muscle will always act to accelerate
muscles,
to the applied
to posture and jumping, gastrocnemius
(i.e., to “Ilex” the ankle)
sensitive to anthropometry lo
and joint angles.
depending
the spanned
corresponding flexion
10 a notion equations
for the body, assuming the body consists of an open articulated chain of either two, three. or four rigid-
general,
ailher direction,
according
We used the dynamic
in the
can act lo
in body positions
to accelerate the ankle towards of induced
acceleration
when the ratio of its knee to ankle moment arm is near the realistic value of 0.5.
is very
Soleus aCtS
‘extencr the knee with much more vigor than itactsto"extend" the ankle.
A HUMAN MUSCULOSKELETAL MODEL FOR PREDICTING ISOMETRIC MUSCULOTENDON TORQUE IN THE SAGITTAL PLANE Melissa G. Hoy, Michael E. Gordon.
and Felix E. Zajac
Rehabilitation Research & Development Center (153), Veterans Adminisaation Medical Center, Palo Alto, CA 94304 and Mechanical Engineering Department. Stanford University, Stanford, CA 94305 Motion of the human body is generated by a complex set of muscles and tendons (musculotendon actuators) that act on the skeletal segments. Computer simulation is necessary to understand how these actuators function and are coordinated during movement. We have developed a musculoskeletal model of the human lower extremity for computer simulation studies of musculotendon function and intermuscular coordination. Our model incorporates the essential properties of muscle and tendon, specifies the musculoskeletal geometry and musculotendon parameters for eighteen lower extremity actuators, and defines the isomeoic torque producing capacity for actuators in the sagittal plane. With our model, we show that musculotendon force and torque depend on actuator-specific musculoskeletal geometry and musculotendon parameters, and that tendon slack length, in particular, has a profound influence on isometric musculotendon function. Neglecting the effect of tendon in analyses of musculotendon force or torque may lead to erroneous predictions of actuator function not only in static situations but during movement as well.
SESSION 3. CARDIOVASCULAR
MECHANICS
WHOLE ORGAN PRESSURE-FLOW RELATIONSHIP IN THE RAT GRACXLIS MUSCLE Don W. Sutton and Geert W. Schmid-Scht(nbein AMES-Bioengineering, University of California - San Diego, La Jolla, California 92093, USA A detailed understanding of blood flow in skeletal muscle requires not only microvascular but whole organ hemodynamic data. Although in the past pressure-flow curves have been obtained for static pressure perfusion, no systematic investigation at both static and dynamic pressures and with different perfusion media has been carried out. With this objective a hemodynamically isolated in-situ gracilis muscle preparation was developed along with a new high precision pulsatile pump to perfuse the muscle. A group of control whole organ pressure-flow curves using a balanced electrolyte solution with 5.2albumin was obtained. Parametric curves were generated by varying the perfusate concentration of Dextran, red blood cells, and white blood cells. The oscillatory capabilities of the pump are utilized to investigate the viscoelastic features of the muscle's vasculature. 10 the vasodilated state, at low pressures, the muscle exhibits a nonlinear pressure flow relationship which becomes linear at higher pressures. These data are highly reproducible and will serve for comparison with a theory of blood flow based on actual gracilis microvessel anatomy and rheology. Supported by NSF grant PCM82-15607.
Abstracts
ACCELERATIONS
OF
HUMAN
LOWER-EXTREMITY JOINTS THEORETICAL CONSIDERATIONS
INDUCED
BY
MUSCLE
FORCES:
Felix E. Zajac, Michael E. Gordon, Melissa G. Hoy, J. Peter Loan Rehabilitation In biomechanical
Research & Development Center (153). Veterans Administration Medical Center, Palo Ano, CA 94304 and Mechanical Englneerfng Department, Stanford University, Slanford. CA 94305-3030 studies of movement.
of how forces in those excited Planar motion body SegmenlS,
muscles
EMG signals recorded
from muscles
act to move the body-segments,
are often interpreted
or joints.
to find the accelerations
of the joints induced by forces in muscles.
on anthropometry
spanned
in the same direction as the applied muscle torque, bul that the unspanned
unspanned accelerate
joints in either
We found that a uniatticular
on the joint angles. direction.
In contrast
joints in directions
Biarticular
and to “extend”
muscles,
to uniarticular
opposite
however,
muscle torques.
However,
accelerations
depend,
of
the direction
muscles,
act lo accelerate
a biarlicular
muscle
For example,
in
the joint
joints will tend to be accelerated
like uniarticular
may act simultaneously
the knee.
These
muscle will always act to accelerate
muscles,
to the applied
to posture and jumping, gastrocnemius
(i.e., to “Ilex” the ankle)
sensitive to anthropometry lo
and joint angles.
depending
the spanned
corresponding flexion
10 a notion equations
for the body, assuming the body consists of an open articulated chain of either two, three. or four rigid-
general,
ailher direction,
according
We used the dynamic
in the
can act lo
in body positions
to accelerate the ankle towards of induced
acceleration
when the ratio of its knee to ankle moment arm is near the realistic value of 0.5.
is very
Soleus aCtS
‘extencr the knee with much more vigor than itactsto"extend" the ankle.
A HUMAN MUSCULOSKELETAL MODEL FOR PREDICTING ISOMETRIC MUSCULOTENDON TORQUE IN THE SAGITTAL PLANE Melissa G. Hoy, Michael E. Gordon.
and Felix E. Zajac
Rehabilitation Research & Development Center (153), Veterans Adminisaation Medical Center, Palo Alto, CA 94304 and Mechanical Engineering Department. Stanford University, Stanford, CA 94305 Motion of the human body is generated by a complex set of muscles and tendons (musculotendon actuators) that act on the skeletal segments. Computer simulation is necessary to understand how these actuators function and are coordinated during movement. We have developed a musculoskeletal model of the human lower extremity for computer simulation studies of musculotendon function and intermuscular coordination. Our model incorporates the essential properties of muscle and tendon, specifies the musculoskeletal geometry and musculotendon parameters for eighteen lower extremity actuators, and defines the isomeoic torque producing capacity for actuators in the sagittal plane. With our model, we show that musculotendon force and torque depend on actuator-specific musculoskeletal geometry and musculotendon parameters, and that tendon slack length, in particular, has a profound influence on isometric musculotendon function. Neglecting the effect of tendon in analyses of musculotendon force or torque may lead to erroneous predictions of actuator function not only in static situations but during movement as well.
SESSION 3. CARDIOVASCULAR
MECHANICS
WHOLE ORGAN PRESSURE-FLOW RELATIONSHIP IN THE RAT GRACXLIS MUSCLE Don W. Sutton and Geert W. Schmid-Scht(nbein AMES-Bioengineering, University of California - San Diego, La Jolla, California 92093, USA A detailed understanding of blood flow in skeletal muscle requires not only microvascular but whole organ hemodynamic data. Although in the past pressure-flow curves have been obtained for static pressure perfusion, no systematic investigation at both static and dynamic pressures and with different perfusion media has been carried out. With this objective a hemodynamically isolated in-situ gracilis muscle preparation was developed along with a new high precision pulsatile pump to perfuse the muscle. A group of control whole organ pressure-flow curves using a balanced electrolyte solution with 5.2albumin was obtained. Parametric curves were generated by varying the perfusate concentration of Dextran, red blood cells, and white blood cells. The oscillatory capabilities of the pump are utilized to investigate the viscoelastic features of the muscle's vasculature. 10 the vasodilated state, at low pressures, the muscle exhibits a nonlinear pressure flow relationship which becomes linear at higher pressures. These data are highly reproducible and will serve for comparison with a theory of blood flow based on actual gracilis microvessel anatomy and rheology. Supported by NSF grant PCM82-15607.