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A biomechanical analysis of load lifting motions
Abstracts
197
ANATOMICAL AND MECHANICAL FACTORS AFFECTING THE STABILITY OF THE HUMAN SPINE
T. WONC, G. MCNEICE, J. RASO and J. ROORDA(University of Waterloo, Waterloo, Ontario, Canada) A 2-D mechanical model was developed to study qualitatively the effects of common anatomical and mechanical factors on the initial buckling load of the adolescent thoracolumbar spine. The model is composed of: (a) two rigid links modelling the thoracic and lumbar spine respectively ; (b) two rotational springs, one between the two links and one at the foundation; and (c) two sets of symmetric cables representing the trunk muscles. It is found that the length ratio (i.e. the ratio of the thoracic to the overall spine iength) is the primary factor affecting the stability of the spine while joint stiffness, muscle stiffness and orientation are of lesser importance. Clinical data collected from the Brace Clinic at the Hospital for Sick Children, Toronto, have indicated also that the progression of scoliosis is connected with high length ratios. SHARK BACKBONE : STRUCTUREAND FIJNC’I-ION
STEM WAINWRK;WT(Zoology Department,
Duke University, Durham, NC 27706)
Shark backbones consist of biconcave vertebral centra made of calcified cartilage separated by capsules of hyaline cartilage filled with fluid and surrounded by a ring of an unidentified refringent acidophil material. The force required to bend whole, dead sharks into radius of curvature observed in slowly swimming sharks (R = 38 cm) is + to f as much as the force to bend the fish into fast swimming arc (R = 20 cm). Bending deformations are elastically recovered upon unloading. The previously undescribed intervertebral structures appear to be responsible for the increase in elastic modulus of the backbone with decrease in radius of curvature. HUMAN SPINAL COLUMN MECHANICS AND INJURY MODES FOLLOWING INITIATION OF SEA’I FiJECIlON LEON
E. KAZARIAN(Aerospace Medical Research Laboratory, Aerospace Medical Division, Air Force Systems Command, Wright-Patterson Air Force Base, Ohio)
The purpose of this overview is to contribute further to our understanding of traumatic vertebral body and intervertebral disk lesions following initiation of the ejection squence. Fractures and dislocations of the spinal column occur with relative frequency as a result of emergency escape from high performance aircraft. Depending on the direction, force, and duration of acceleration, the vertebral centra, neural arch, intervertebral disks along with the content of the spinal canal may be affected. The form and extent of spinal injury depends largely upon the internal resistance afforded by the vertebral structure which varies throughout the length of the spinal column. In this presentation the various frames of reference of the open ejection seat are identified. Human body kinetics due to + G, forces are characterized. The types of spinal column lesions are classified and correlated to ejection seat accelerations, man seat separation, parachute opening shock and ground landing impact. GSnMATION AND MEASUREMENT OF LOADS ON THE LUMBAR SPINE A. B. SCHULTZ, G.
B. J. ANDERSSON, R. ~RTENGREN and A. L. NACHEMSON (UICC, Box 4348, Chicago, IL 60680, and Sahlgren Hospital, Gothenburg, Sweden)
A series of isometric standing and seated work activities were analyzed to determine what loads they imposed on the trunk. Internal loads were predicted from equilibrium considerations. In corresponding experiments, surface myoelectric activity was measured at twelve locations in ten subjects, and in three additional subjects, intra-discal and intra-gastric pressures were measured as well. Good agreement was found between the predicted muscle contraction forces and the myoelectric signal levels, and between the predicted spine compression forces and the intradiscal pressure levels. The loads on the spine can be adequately predicted using simple biomechanical models, or can be experimentally determined from indirect measurements. A BIOMECHANICAL ANALYSIS OF LOAD LIFITNG MOTIONS DON
B. CHAFFINand ARUN GARG (Ergonomics Laboratory, 2254 G. G. Brown Laboratory, The University of Michigan, Ann Arbor, MI 48109)
This paper presents a study of the motion dynamics involved in lifting maximum loads from floor to table height. Subjects selected their maximum loads psychophysically, i.e. by adding or subtracting lead shot from four different size containers which have an unknown weight added before each session. During both the initial and final trials in each session, stroboscopic photographs and force platform data were obtained.
198
Abstracts
These data are used in a seven link biomechanical model to determine how the articulation load moments vary with (1) load lifted, (2) size of container, (3) practice, and (4) muscle strengths as determined by isometric tests. It is proposed that such information is important in determining lifting postures and load characteristics which produce strain/sprain injuries in industry. POWER OUTPUT AS A FUNCTION OF LOAD VARIATTON IN OLYMPIC AND POWER LIFlTNG JOHN
GARHAMMER (Biomechanics Laboratory, Department of Kinesiology, UCLA, Los Angeles, CA 90024) THOMAS MCLAUGHLIN (Biomechanics Laboratory, Auburn University, Auburn, AL 36830) Strength and power are of major importance in competitive lifting and many sports. The purpose of this study was to collect information on power production during several lifting movements and to examine its variation with load changes. Data were obtained from 16 mm fihns taken at 50 fps at numerous national and international lifting championships. Situations were picked for study where a given lifter made two successfullifts of one type. The highest weight lifted in a meet was considered a looO/,effort. Results showed that power outputs for athletes of similar bodyweights were two to three times higher in snatches and cleans than in squats and deadlifts. All situations analyzed involving these four lifts showed higher power outputs for the submaximal load 900 watts were developed for a 4112 N squat vs 1259W for a 93% effort. Similarly, 2173 W were produced during a 1396N snatch vs 2298 at 98% effort Information of this type should be very important to both competitive lifters and athletes choosing training lifts and weights to be used for the development of strength and/or power. DEVELOPING A STRATEGY TO IDENTIFY THE TJXHNKAL JAMES G.
FACTORS LIMITING PERFORMANCE
HAY(Biomechanics Laboratory, Department of Physical Education, University of Iowa, Iowa City, Iowa)
The purposes of this paper are (1) to review previous attempts to identify objectively the limiting factors in the performance of a motor skill and (2) to present a progress report on an alternative systematic procedure. The attempts which have been made to improve performance via biomechanical analysis have usually involved use of the empirical method or the mathematical modelling method. The alternative procedure presented consists of three steps: (1) the development of a deterministic model linking the performance to the underlying technical factors upon which it is based, (2) the gathering of data on a representative sample and (3) the analysis of that data to identify and order those technical factors which limit the quality of the perfornmmx. KINETICS OF POSTURAL CONTROL IN MAN KEITH
C. HAYES,PATRICE L. WEISSand WARREN G. DARLING(University of Waterloo, Department of Kinesiology, Ontario, Canada)
A rigid-body linked-segment kinetic analysis of the muscular torques required to stabilize the trunk and legs during arm movement has revealed that the pattern of preparatory postural muscle activity (a postural “motor programme”) is predictable from, and at the same time determined by, the dynamics of the forthcoming arm movement. It has also indicated that the preparatory muscle activity serves to reduce the disturbance to the centre of gravity and the energy cost of postural adjustments (where the instantaneous energy of each body segment is given by El = l/2 rn{u:+ l/2 I,& + m&,). Finally, the preparatory postural muscular torques are organized in “functional pairs” (Nashner, 1978); specifically, functional synergies have been identified in the erector spinae and hamstring muscle groups and in quadriceps and rectus abdominus. COMPARATIVE SIOMECHAMCAL ANALYSIS OF THE SUBTROCHANTERlC AND INTRRTROCHANTERIC OSTROTOMIRS ALAN L.
BRIXDand R-H G. NARECHANIA (Division of Orthopedic Surgery, University of Wisconsin Hospitals, Madison, WI 53792)
This investigation compares the theoretical effects of subtrochanteric and intertrochanteric femoral osteotomy on the relationship of the lengths of iliopsoas, gluteus medius, gluteus minimus and gluteus maximus muscles. These proximal femoral osteotomies are fraquently performed for femoral anteversion or valgus in the treatment of congenital dislocation of the hip, the hip in cerebral palsy, paralytic disease and persistent foetal alignment. The hypothesis is made that the tension of these muscles changed with the change in bony alignment and this study shows the theoretical changes.
197
ANATOMICAL AND MECHANICAL FACTORS AFFECTING THE STABILITY OF THE HUMAN SPINE
T. WONC, G. MCNEICE, J. RASO and J. ROORDA(University of Waterloo, Waterloo, Ontario, Canada) A 2-D mechanical model was developed to study qualitatively the effects of common anatomical and mechanical factors on the initial buckling load of the adolescent thoracolumbar spine. The model is composed of: (a) two rigid links modelling the thoracic and lumbar spine respectively ; (b) two rotational springs, one between the two links and one at the foundation; and (c) two sets of symmetric cables representing the trunk muscles. It is found that the length ratio (i.e. the ratio of the thoracic to the overall spine iength) is the primary factor affecting the stability of the spine while joint stiffness, muscle stiffness and orientation are of lesser importance. Clinical data collected from the Brace Clinic at the Hospital for Sick Children, Toronto, have indicated also that the progression of scoliosis is connected with high length ratios. SHARK BACKBONE : STRUCTUREAND FIJNC’I-ION
STEM WAINWRK;WT(Zoology Department,
Duke University, Durham, NC 27706)
Shark backbones consist of biconcave vertebral centra made of calcified cartilage separated by capsules of hyaline cartilage filled with fluid and surrounded by a ring of an unidentified refringent acidophil material. The force required to bend whole, dead sharks into radius of curvature observed in slowly swimming sharks (R = 38 cm) is + to f as much as the force to bend the fish into fast swimming arc (R = 20 cm). Bending deformations are elastically recovered upon unloading. The previously undescribed intervertebral structures appear to be responsible for the increase in elastic modulus of the backbone with decrease in radius of curvature. HUMAN SPINAL COLUMN MECHANICS AND INJURY MODES FOLLOWING INITIATION OF SEA’I FiJECIlON LEON
E. KAZARIAN(Aerospace Medical Research Laboratory, Aerospace Medical Division, Air Force Systems Command, Wright-Patterson Air Force Base, Ohio)
The purpose of this overview is to contribute further to our understanding of traumatic vertebral body and intervertebral disk lesions following initiation of the ejection squence. Fractures and dislocations of the spinal column occur with relative frequency as a result of emergency escape from high performance aircraft. Depending on the direction, force, and duration of acceleration, the vertebral centra, neural arch, intervertebral disks along with the content of the spinal canal may be affected. The form and extent of spinal injury depends largely upon the internal resistance afforded by the vertebral structure which varies throughout the length of the spinal column. In this presentation the various frames of reference of the open ejection seat are identified. Human body kinetics due to + G, forces are characterized. The types of spinal column lesions are classified and correlated to ejection seat accelerations, man seat separation, parachute opening shock and ground landing impact. GSnMATION AND MEASUREMENT OF LOADS ON THE LUMBAR SPINE A. B. SCHULTZ, G.
B. J. ANDERSSON, R. ~RTENGREN and A. L. NACHEMSON (UICC, Box 4348, Chicago, IL 60680, and Sahlgren Hospital, Gothenburg, Sweden)
A series of isometric standing and seated work activities were analyzed to determine what loads they imposed on the trunk. Internal loads were predicted from equilibrium considerations. In corresponding experiments, surface myoelectric activity was measured at twelve locations in ten subjects, and in three additional subjects, intra-discal and intra-gastric pressures were measured as well. Good agreement was found between the predicted muscle contraction forces and the myoelectric signal levels, and between the predicted spine compression forces and the intradiscal pressure levels. The loads on the spine can be adequately predicted using simple biomechanical models, or can be experimentally determined from indirect measurements. A BIOMECHANICAL ANALYSIS OF LOAD LIFITNG MOTIONS DON
B. CHAFFINand ARUN GARG (Ergonomics Laboratory, 2254 G. G. Brown Laboratory, The University of Michigan, Ann Arbor, MI 48109)
This paper presents a study of the motion dynamics involved in lifting maximum loads from floor to table height. Subjects selected their maximum loads psychophysically, i.e. by adding or subtracting lead shot from four different size containers which have an unknown weight added before each session. During both the initial and final trials in each session, stroboscopic photographs and force platform data were obtained.
198
Abstracts
These data are used in a seven link biomechanical model to determine how the articulation load moments vary with (1) load lifted, (2) size of container, (3) practice, and (4) muscle strengths as determined by isometric tests. It is proposed that such information is important in determining lifting postures and load characteristics which produce strain/sprain injuries in industry. POWER OUTPUT AS A FUNCTION OF LOAD VARIATTON IN OLYMPIC AND POWER LIFlTNG JOHN
GARHAMMER (Biomechanics Laboratory, Department of Kinesiology, UCLA, Los Angeles, CA 90024) THOMAS MCLAUGHLIN (Biomechanics Laboratory, Auburn University, Auburn, AL 36830) Strength and power are of major importance in competitive lifting and many sports. The purpose of this study was to collect information on power production during several lifting movements and to examine its variation with load changes. Data were obtained from 16 mm fihns taken at 50 fps at numerous national and international lifting championships. Situations were picked for study where a given lifter made two successfullifts of one type. The highest weight lifted in a meet was considered a looO/,effort. Results showed that power outputs for athletes of similar bodyweights were two to three times higher in snatches and cleans than in squats and deadlifts. All situations analyzed involving these four lifts showed higher power outputs for the submaximal load 900 watts were developed for a 4112 N squat vs 1259W for a 93% effort. Similarly, 2173 W were produced during a 1396N snatch vs 2298 at 98% effort Information of this type should be very important to both competitive lifters and athletes choosing training lifts and weights to be used for the development of strength and/or power. DEVELOPING A STRATEGY TO IDENTIFY THE TJXHNKAL JAMES G.
FACTORS LIMITING PERFORMANCE
HAY(Biomechanics Laboratory, Department of Physical Education, University of Iowa, Iowa City, Iowa)
The purposes of this paper are (1) to review previous attempts to identify objectively the limiting factors in the performance of a motor skill and (2) to present a progress report on an alternative systematic procedure. The attempts which have been made to improve performance via biomechanical analysis have usually involved use of the empirical method or the mathematical modelling method. The alternative procedure presented consists of three steps: (1) the development of a deterministic model linking the performance to the underlying technical factors upon which it is based, (2) the gathering of data on a representative sample and (3) the analysis of that data to identify and order those technical factors which limit the quality of the perfornmmx. KINETICS OF POSTURAL CONTROL IN MAN KEITH
C. HAYES,PATRICE L. WEISSand WARREN G. DARLING(University of Waterloo, Department of Kinesiology, Ontario, Canada)
A rigid-body linked-segment kinetic analysis of the muscular torques required to stabilize the trunk and legs during arm movement has revealed that the pattern of preparatory postural muscle activity (a postural “motor programme”) is predictable from, and at the same time determined by, the dynamics of the forthcoming arm movement. It has also indicated that the preparatory muscle activity serves to reduce the disturbance to the centre of gravity and the energy cost of postural adjustments (where the instantaneous energy of each body segment is given by El = l/2 rn{u:+ l/2 I,& + m&,). Finally, the preparatory postural muscular torques are organized in “functional pairs” (Nashner, 1978); specifically, functional synergies have been identified in the erector spinae and hamstring muscle groups and in quadriceps and rectus abdominus. COMPARATIVE SIOMECHAMCAL ANALYSIS OF THE SUBTROCHANTERlC AND INTRRTROCHANTERIC OSTROTOMIRS ALAN L.
BRIXDand R-H G. NARECHANIA (Division of Orthopedic Surgery, University of Wisconsin Hospitals, Madison, WI 53792)
This investigation compares the theoretical effects of subtrochanteric and intertrochanteric femoral osteotomy on the relationship of the lengths of iliopsoas, gluteus medius, gluteus minimus and gluteus maximus muscles. These proximal femoral osteotomies are fraquently performed for femoral anteversion or valgus in the treatment of congenital dislocation of the hip, the hip in cerebral palsy, paralytic disease and persistent foetal alignment. The hypothesis is made that the tension of these muscles changed with the change in bony alignment and this study shows the theoretical changes.