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Influence of passive elastic joint moments on human gait
Abstracts
87Y
The Piola-Kirchhoff stress is determined from a constitutive relation which involves five moduli characterizing a transverse isotropic and inhomogeneous myocardium with preferred fiber orientation. In addition to the equation of motion, this stress, which is relative to the undeformed configuration at aortic valve closure, fulfills angular momentum of the ventricle, the principle of frame indifference, endocardial condition ofcavity pressure, and epicardial condition of pleural-pericardial pressure. The Cauchy stress is then evaluated with respect to the deformed configuration at mitral valve opening. The ventricular surface is assumed regular, and the region occupied is simply-connected by a cut which when approached on either side, the finite strain tensor implies the same displacement field. A LASER SCANNING
SYSTEM FOR TRACKING MOTION IN THREE-DIMENSIONAL FOR BIOMECHANICAL APPLICATIONS
JANE F. MACFARLAXEand MAX DONATH (Department of Mechanical Engineering, Minnesota, Minneapolis, MN 55455, U.S.A.)
SPACE
University of
A new approach for measuring the motion of a body in three-dimensional space has been developed. The threedimensional location ofa target is determined by scanninga target field with three planes of laser light. Laser light sensitive detectors are used to sense the laser scan. By tracking three noncolinear detectors attached to a rigid body, the position and orientation of the body is determined. The present implementation is for a 6 feet x 6 feet x 4 feet target field in order to track motion of the human torso and extremities. The position error is less than 0. I inches. The system is self calibrating and provides a data rate of 480 (x, y, z) points per second pet targeted point. Three such points will determine the position and orientation of the attached limb segment. Knowing the position and orientation of two adjacent limb segments, the instantaneous center of rotation of a joint and the contoured angle can be calculated. A two-dimensional system is presently operational. The three-dimensional case is a natural extension with the necessary modifications presently underway. INFLUENCE
OF PASSIVE ELASTIC JOINT MOMENTS
ON HUMAN
GAIT
J. M. MANSOURand M. AUDU (Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106, U.S.A.) The passive elastic moment at the knee was measured over a range of knee angles selected to include those found in normal gait. Each measurement of passive knee moment was made with the hip and ankle at specified angles; - lo”, O’, 10’ for the foot and O”, IO” of hip flexion. Four normal adult male subjects were studied. The passive moments at the knee were compared to the total knee moment computed for normal walking. The results showed that the passive moment at the knee was a significant percentage (30 %-IO0 ?i) of the total joint moment at toe off and heel strike. Some caution must be exercised in analyzing these results since the passive and total moment data were not obtained from the same subject. However, the high contribution of the passive moment 10 the total moment does not appear to be insignificant. THE SENSITIVITY
OF SKIN STRENGTH
TO STRAIN RATE OF LOADING
ROGER C. HAUT (General Motors Research Laboratories, Biomedical Science Department, Section, Warren, MI 48090, U.S.A.)
Crash Injury
The sensitivity of tensile strength and failure strain to strain rate was studied for dorsal rat skin. Dumb-bell shaped test specimens were cut parallel to the spine from skin flaps of Fischer rats aged 1-27 months, and stretched until failure at high (1350mm s-‘)and low (6.75 mm s-‘) speeds. The sensitivity to rate ofstrain was measured as the ratio of failure parameters at high to low speed. The sensitivity of tensile strength to strain rate decreased during growth and sexual maturation, and remained constant thereafter. Failure strain was insensitive to rate of loading at all ages. While static tensile strength correlated with concentration of tissue collagen, sensitivity of the tissue to strain rate paralleled concentration of glycosaminoglycans (GAG) to collagen. Although the mechanism of strain-rate-sensitivity is not understood, interaction of collagen fibrils with the matrix of GAG is likely an important factor. THE 20 MHz PULSED ULTRASONIC DOPPLER VELOCITY METER: A METHOD ASSESSING FLOW IN SMALL VESSELS
FOR
WILLIAM F. BLAIR (Department of Orthopaedics, University of Iowa, Iowa City, IA 52242, U.S.A.) DOUGLASR. PEDERSEN(Orthopaedic Biomechanics Laboratory, University of Iowa, Iowa City, IA 52242, U.S.A.) The quantification of blood flow in microsurgical models is a difficult goal to accomplish. The 20 MHZ pulsed ultrasonic Doppler velocity meter (PUDVM) is an instrument which reproducibly and precisely accomplishes
87Y
The Piola-Kirchhoff stress is determined from a constitutive relation which involves five moduli characterizing a transverse isotropic and inhomogeneous myocardium with preferred fiber orientation. In addition to the equation of motion, this stress, which is relative to the undeformed configuration at aortic valve closure, fulfills angular momentum of the ventricle, the principle of frame indifference, endocardial condition ofcavity pressure, and epicardial condition of pleural-pericardial pressure. The Cauchy stress is then evaluated with respect to the deformed configuration at mitral valve opening. The ventricular surface is assumed regular, and the region occupied is simply-connected by a cut which when approached on either side, the finite strain tensor implies the same displacement field. A LASER SCANNING
SYSTEM FOR TRACKING MOTION IN THREE-DIMENSIONAL FOR BIOMECHANICAL APPLICATIONS
JANE F. MACFARLAXEand MAX DONATH (Department of Mechanical Engineering, Minnesota, Minneapolis, MN 55455, U.S.A.)
SPACE
University of
A new approach for measuring the motion of a body in three-dimensional space has been developed. The threedimensional location ofa target is determined by scanninga target field with three planes of laser light. Laser light sensitive detectors are used to sense the laser scan. By tracking three noncolinear detectors attached to a rigid body, the position and orientation of the body is determined. The present implementation is for a 6 feet x 6 feet x 4 feet target field in order to track motion of the human torso and extremities. The position error is less than 0. I inches. The system is self calibrating and provides a data rate of 480 (x, y, z) points per second pet targeted point. Three such points will determine the position and orientation of the attached limb segment. Knowing the position and orientation of two adjacent limb segments, the instantaneous center of rotation of a joint and the contoured angle can be calculated. A two-dimensional system is presently operational. The three-dimensional case is a natural extension with the necessary modifications presently underway. INFLUENCE
OF PASSIVE ELASTIC JOINT MOMENTS
ON HUMAN
GAIT
J. M. MANSOURand M. AUDU (Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106, U.S.A.) The passive elastic moment at the knee was measured over a range of knee angles selected to include those found in normal gait. Each measurement of passive knee moment was made with the hip and ankle at specified angles; - lo”, O’, 10’ for the foot and O”, IO” of hip flexion. Four normal adult male subjects were studied. The passive moments at the knee were compared to the total knee moment computed for normal walking. The results showed that the passive moment at the knee was a significant percentage (30 %-IO0 ?i) of the total joint moment at toe off and heel strike. Some caution must be exercised in analyzing these results since the passive and total moment data were not obtained from the same subject. However, the high contribution of the passive moment 10 the total moment does not appear to be insignificant. THE SENSITIVITY
OF SKIN STRENGTH
TO STRAIN RATE OF LOADING
ROGER C. HAUT (General Motors Research Laboratories, Biomedical Science Department, Section, Warren, MI 48090, U.S.A.)
Crash Injury
The sensitivity of tensile strength and failure strain to strain rate was studied for dorsal rat skin. Dumb-bell shaped test specimens were cut parallel to the spine from skin flaps of Fischer rats aged 1-27 months, and stretched until failure at high (1350mm s-‘)and low (6.75 mm s-‘) speeds. The sensitivity to rate ofstrain was measured as the ratio of failure parameters at high to low speed. The sensitivity of tensile strength to strain rate decreased during growth and sexual maturation, and remained constant thereafter. Failure strain was insensitive to rate of loading at all ages. While static tensile strength correlated with concentration of tissue collagen, sensitivity of the tissue to strain rate paralleled concentration of glycosaminoglycans (GAG) to collagen. Although the mechanism of strain-rate-sensitivity is not understood, interaction of collagen fibrils with the matrix of GAG is likely an important factor. THE 20 MHz PULSED ULTRASONIC DOPPLER VELOCITY METER: A METHOD ASSESSING FLOW IN SMALL VESSELS
FOR
WILLIAM F. BLAIR (Department of Orthopaedics, University of Iowa, Iowa City, IA 52242, U.S.A.) DOUGLASR. PEDERSEN(Orthopaedic Biomechanics Laboratory, University of Iowa, Iowa City, IA 52242, U.S.A.) The quantification of blood flow in microsurgical models is a difficult goal to accomplish. The 20 MHZ pulsed ultrasonic Doppler velocity meter (PUDVM) is an instrument which reproducibly and precisely accomplishes