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Individual trunk muscle and ligament forces during dynamic lifting
742
Abstracts-International
Society
of Biomechanics
XIII
Congress
1991
COMPUTEB GRAPHICS AND ANIMA!l!ION IN BIOMJXHANICAL EVALUATION OF WORK -ANDMOvEMENTs Roland drtengren and Gunnar Nilsson, Department of Injury Prevention, Chalmers University of Technology, S-412 96 Gijteborg, Sweden The purpose of this project is to develop methods and procedures for graphic simulation and ergonomic evaluation of work as a tool for engineers. A system is built up consisting of a modeller, a multi body systems analysis module, a data base for object storage, and an anthrop+ metric human body model. Product models to be assembled are obtained from the CAD-system in which they are designed. The ergonomic evaluation includes analysis of space requirements, reach distances, visual obstacles or constraints and comfort angles of joints. Biomechanical calculations are also made resulting in data which describe the instantaneous torque and resultant force on joints and body segments as functions of time. These values can be compared with tissue strength data and maximal capacities for force exertion. The lower the values the better, but the time course must also be considered and an integrated value representing the dose of load on each joint calculated. When the loading on one joint must be traded against another, an optimization procedure could be used to reach a favourable loading situation provided that a suitable criterion can be formulated. At present no such criteria have been tested, however. The control of the animation presents particular requirements depending on the number of degrees of freedom of the body model. When the number is low, key frame animation can be used. When it gets higher it becomes very tedious to control each degree of freedom separately, then, for example, gesture control or algorithmic animation must be used.
A NEW BIOMECHANICAL TECHNIQUE FOR INCREASING OF JOINT FLEXIBILITY WITH A FOCUS ON BACK PAIN PREVENTION Mark R. Pitkin Newman Laboratory for Biomechanics and Human Rehabilitation, Department of Mechanical Engineering, Massachusetts Intstitute of Technology, Cambridge, MA 02139, USA A new approach to the flexibility of joints, based on understanding of Yoga success is presented. We use a term “Savasana Principle” (SP) dealing with stress by fixating posture following by relaxation. It was found, that SP, sequentially applied, can increase the range of motion of the same joint or group of joints. A technique was developed for training people in increasing of their flexibility. Since the flexibility of the spine is considered as a key point for prevention of the back pain, a modified car seat and similar training device could be used to faciliate flexibility. Sixteen volunteers both male and female of age from 33 to 67 were selected which could not touch a floor with their fingers by bending a torso without flexing knee joints. Everybody, including those who never reach the floor, could touch the floor in several attempts of using SP (from three to nine times individually). The best results were achieved when the subject’s back was held by sertain assistance during the stress phases: “Car Seat Principle” (CSP).
INDIVIDUAL
TRUNK MUSCLE AND LIGAMENT
FORCES DURING DYNAMIC LIFTING
J.R. Potvin, SM. McGill, R.W. Norman Department of Kinesiology, University of Waterloo Waterloo, Ontario, Canada A study was conducted to estimate the time-history of the forces produced by the various trunk muscles and ligaments for nine male subjects during lifting with fiie loads (ranging from 5.8 to 32.4 kg) and two techniques (stoop and squat). These forces were calculated with a biomechanical model which used EMG and spine kinematics to partition the L4/w reaction moment into muscle and ligament components respectively. The forces produced by the abdominal muscle groups were low for all load conditions studied. Ligament forces were relatively low and consistent across loads and their subsequent peak extensor moments were almost always below 50 N m. The larger degree of trunk flexion associated with the stoop lifting technique resulted in higher ligament forces and lower extensor muscle forces when compared with the squat technique results. However, for both styles of lifting the extensor musculature was found to be responsible for increasing their forces to meet an increasing extensor moment demand with higher loads.
Abstracts-International
Society
of Biomechanics
XIII
Congress
1991
COMPUTEB GRAPHICS AND ANIMA!l!ION IN BIOMJXHANICAL EVALUATION OF WORK -ANDMOvEMENTs Roland drtengren and Gunnar Nilsson, Department of Injury Prevention, Chalmers University of Technology, S-412 96 Gijteborg, Sweden The purpose of this project is to develop methods and procedures for graphic simulation and ergonomic evaluation of work as a tool for engineers. A system is built up consisting of a modeller, a multi body systems analysis module, a data base for object storage, and an anthrop+ metric human body model. Product models to be assembled are obtained from the CAD-system in which they are designed. The ergonomic evaluation includes analysis of space requirements, reach distances, visual obstacles or constraints and comfort angles of joints. Biomechanical calculations are also made resulting in data which describe the instantaneous torque and resultant force on joints and body segments as functions of time. These values can be compared with tissue strength data and maximal capacities for force exertion. The lower the values the better, but the time course must also be considered and an integrated value representing the dose of load on each joint calculated. When the loading on one joint must be traded against another, an optimization procedure could be used to reach a favourable loading situation provided that a suitable criterion can be formulated. At present no such criteria have been tested, however. The control of the animation presents particular requirements depending on the number of degrees of freedom of the body model. When the number is low, key frame animation can be used. When it gets higher it becomes very tedious to control each degree of freedom separately, then, for example, gesture control or algorithmic animation must be used.
A NEW BIOMECHANICAL TECHNIQUE FOR INCREASING OF JOINT FLEXIBILITY WITH A FOCUS ON BACK PAIN PREVENTION Mark R. Pitkin Newman Laboratory for Biomechanics and Human Rehabilitation, Department of Mechanical Engineering, Massachusetts Intstitute of Technology, Cambridge, MA 02139, USA A new approach to the flexibility of joints, based on understanding of Yoga success is presented. We use a term “Savasana Principle” (SP) dealing with stress by fixating posture following by relaxation. It was found, that SP, sequentially applied, can increase the range of motion of the same joint or group of joints. A technique was developed for training people in increasing of their flexibility. Since the flexibility of the spine is considered as a key point for prevention of the back pain, a modified car seat and similar training device could be used to faciliate flexibility. Sixteen volunteers both male and female of age from 33 to 67 were selected which could not touch a floor with their fingers by bending a torso without flexing knee joints. Everybody, including those who never reach the floor, could touch the floor in several attempts of using SP (from three to nine times individually). The best results were achieved when the subject’s back was held by sertain assistance during the stress phases: “Car Seat Principle” (CSP).
INDIVIDUAL
TRUNK MUSCLE AND LIGAMENT
FORCES DURING DYNAMIC LIFTING
J.R. Potvin, SM. McGill, R.W. Norman Department of Kinesiology, University of Waterloo Waterloo, Ontario, Canada A study was conducted to estimate the time-history of the forces produced by the various trunk muscles and ligaments for nine male subjects during lifting with fiie loads (ranging from 5.8 to 32.4 kg) and two techniques (stoop and squat). These forces were calculated with a biomechanical model which used EMG and spine kinematics to partition the L4/w reaction moment into muscle and ligament components respectively. The forces produced by the abdominal muscle groups were low for all load conditions studied. Ligament forces were relatively low and consistent across loads and their subsequent peak extensor moments were almost always below 50 N m. The larger degree of trunk flexion associated with the stoop lifting technique resulted in higher ligament forces and lower extensor muscle forces when compared with the squat technique results. However, for both styles of lifting the extensor musculature was found to be responsible for increasing their forces to meet an increasing extensor moment demand with higher loads.