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    bahan multiplier bahan multiplier Document Transcript

    • Formål At give indsigt i Biomekanik i relation til design og Applied konstruktion af apparater Indhold Biomechanics Newton mekanik Biomekaniske målemetoder Antropometri Idræt Ergonomi Modellering Pascal Madeleine AB Applied Biomechanics mm 5 Human factors and systems Applications in Ergonomics Anthropometri Concepts Cumulative trauma disorders – repetitive stress injuries mm 7 Applications in Ergonomics Concepts, cumulative disorders mm 8 Optimization in Ergonomics mm7 AB Pascal Madeleine Definition History Domains of specialization Holistic approach in which considerations of physical, Taylor and Gilbreth showed how a task can be cognitive, social, organizational, environmental and broken down into a number of identifiable, discrete other relevant factors are taken into account. There exist domains of specialization within the steps that can be characterized by: discipline, which represent deeper competencies in - type of physical motion specific human attributes or characteristics of human - energy expenditure interaction. - time required to accomplish the task - Physical ergonomics - Cognitive ergonomics Increase productivity - Organizational ergonomics
    • Definition How the body works in working situations? Domains of specialization Physical ergonomics Anatomy, physiology, biomechanics, anthropometry, … The body like en engine – Fueling and cooling system Cognitive ergonomics moves supplies to combustion sites (muscles and Memory, computer interface, instrument design, stress, organs) and removes combustion by-products (lactic user interface, … acid, carbon dioxide,…) for dissipation (skin and lungs). Organizational ergonomics Working situations, rotation,working hours, … Control systems: respiratory system, circulatory system, metabolic system Assessment Assessment of energy of energy expenditures expenditures at work at work Assessment of energy expenditures Assessment at work of energy expenditures at work
    • Exposure-Response-Effect How the body interacts with Model the environment? Load Physical Individual Thermoregulation work factors Biomechanical Responses Working in cold Tolerance and hot Organisational environment factors Subjective Air pollution Physiological Responses Responses Altitude (Pain, Discomfort) Noise Social Injury context Gravity Vibrations Disability Radiations … Exposure-Response-Effect Model Pain in Europe European survey 46,000 interviews in 16 European Load countries Biomechanical Responses Tolerance Subjective Physiological Responses Responses (Pain, Discomfort) Injury Disability Cumulative trauma disorders Cumulative trauma disorders (CTDs) (CTDs) CTDs is commonly known as work-related disorders of You've heard it called Repetitive Strain Injury (RSI) the head and upper extremities and are caused when and Carpal Tunnel Syndrome. there is sufficient stress in a tissue to cause a pathologic It is also known as: Tendinitis, Tennis Elbow or change in that tissue. Epicondylitis, DeQuervain's Disease, and Thoracic Examples of common CTD injuries: Outlet Syndrome. It causes pain and discomfort in the - tendinitis - Carpal Tunnel Syndrome neck, shoulders, wrists, forearms, fingers, elbows, and - fibromyalgia - synovitis/bursitis back. It can be disabling. CTDs is the current name for a collections of symptoms which can be found in the medical literature occurring Not really treatable but it is preventable. in standardists/musicians from as early the early 1800’s (Fry, 1986)
    • Cumulative trauma disorders CTDs (CTDs) CTDs can be divided into separate causative factors: Use of Excessive Force: CTD is a wear-and-tear injury to the soft muscle tissue. Due to inexperience, improper supervision, a belief that more It is caused by continual stress to specific tendons, force does a better job, competition on the line among workers, joints, or muscles. Stress is induced by repetition, force, broken or faulty equipment, poorly designed equipment vibration, and cold. Your body is stressed by daily living activities. If your body is not able to recover from these Fixed Working Postures: stressful activities, it will no longer tolerate them. Prolonged periods of static posture. CTD is linked to work-related activities (writing, Speed of Workers' Movements: typing, assembly, tool use). Piece or machine-paced work However, nonoccupational like body weight, pre- existing injuries, physical fitness, smoking, gender, age Psychosocial Stress and health conditions (diabetes, arthritis) are of importance. CTDs CTDs Local Fatigue Systemic Fatigue Listed below are the categories of the body in which the There may be any combination of the following signs resultant symptomatology is described, due to local and symptoms when systemic fatigue is involved with or fatigue: without local fatigue, although local almost always precedes systemic: • Biomechanical •general feelings of fatigue; •inability to sleep leading anxiety and/or irritability; • Tenderness and pain •general feeling of heaviness or lack of mobility; •general or specific pain that has been described as • Circulatory problem constant or intermittent dull pain, sharp and/or shooting sensations. • Neurophysiological MMH Analysis of working situations Heavy work (lift) Repetitive work (ensidigt gentaget arbejde) Slaughterhouse – Refuse collection – Computer work – Manual material handling – Vibrations … COLLABORATION WITH ERGOMAT A/S
    • Model Risk factors Both physical and psychosocial factors are of interest and will influence the outcome. OCCUPATIONAL The known physical factors are: MOTOR SETTINGS - relatively fixed erect posture, CONTROL - repetitive arm movements, - heavy work, - insufficient rest, - static posture and - vibrations PAIN IN - cold DEEP STRUCTURE Exposure-response-effect (2) Back (Sjøgaard 1995) Exposure -Mental External Factors -Physical Internal Factors Acute Response -ATP-ase -Actin-Myosin Coupling -Etc… Individual Factors Long Term Effects Adaptation WMSD - Chronic effects Risk factors Low back pain Both physical and psychosocial factors are of interest and will influence the outcome. Pain in lower back coming from the spine, muscles, nerves, or other structures in that region of your back. The known physical factors are: It may also radiate from other areas. - relatively fixed erect posture, - repetitive arm movements, Variety of symptoms: tingling or burning sensation, a - heavy work, dull aching, or sharp pain. Evt. weakness in your legs or - insufficient rest, feet. - static posture and - vibrations Not necessarily caused by one event. One may have been doing many things improperly for a long time. Then suddenly, one simple movement leads to the feeling of pain.
    • National institute for Low back pain occupational safety and health (NIOSH) lifting equation The specific structure in your back responsible for your pain is hardly ever identified. 1 The equation and its function There are several possible sources of low back pain: 2 Task data or variables * Small fractures to the spine from osteoporosis * Muscle spasm (very tense muscles that remain contracted) 3 Multipliers * Ruptured or herniated disk 4 Design/redesign using the recommended weight limit * Degeneration of the disks and lifting index * Poor alignment of the vertebrae 5 Limitations * Spinal stenosis (narrowing of the spinal canal) 6 Single task and multitasks assessments * Strain or tears to the muscles or ligaments supporting the back Revised 1991 NIOSH Lifting Equation * Spine curvatures (like scoliosis or kyphosis) * Other medical conditions like fibromyalgia THE EQUATION AND ITS THE EQUATION AND ITS FUNCTION FUNCTION Recommended Weight Limit (RWL) Recommended Weight Limit (RWL) The RWL is the weight of the load that nearly all healthy workers could perform in a specific set of task RWL = LC x HM x VM x DM x AM x FM x CM conditions over a substantial period of time (eg. up to 8 hours) without an increased risk of developing lifting- Where : LC Load Constant = 23 kg. related low back pain. HM Horizontal Multiplier (distance from object to worker) Based on a multiplicative model providing a weighting VM Vertical Multiplier (distance from hands to floor) for each of six task variables. The weightings are DM Distance Multiplier (lift distance) AM Asymmetric Multiplier (lift asymmetry) expressed as coefficients that serve to decrease the load FM Frequency Multiplier (duration and frequency) constant. CM Coupling Multiplier (good, medium or bad handgrip) The load constant represents the maximum The term multipliers refers to the reduction coefficients that serve to decrease the load constant. recommended load weight to be lifted under ideal THE EQUATION AND ITS TASK DATA OR VARIABLES FUNCTION It refers to the task descriptors (ie. Horizontal location, Vertical location, Distance of travel, Asymmetric angle, Lifting index (LI) Frequency rates and Coupling) that are measurable. LI provides a relative estimate of the level of physical stress associated with a particular manual lifting task. Horizontal Location (H) Load Weight (L) LI = H is measured from the mid-point of the line joining the Recommended Weight Limit (RWL) inner ankle bones to a point projected on the floor directly below the mid-point of the hand grasps (ie. load Load Weight (L) = weight of the object lifted. center), as defined by the large middle knuckle of the hand. Lifting tasks with LI>1.0 pose an increased risk for H should be measured or approximated from the lifting-related low back pain. following equations : If LI=3, nearly all workers risk to develop a work- 1) for V = >25 cm H = 20 cm + W/2 related injury. 2) for V <25 cm H = 25 cm + W/2 Where W is the width of the container in the sagittal plane and V is the
    • TASK DATA TASK DATA OR VARIABLES OR VARIABLES Vertical Location (V) V is defined as the vertical location of the hands above the floor at origin of lift. V is measured vertically from the floor to the mid-point between the hand grasps, as defined by the large middle knuckle. Vertical Travel Distance (D) D is defined as the vertical travel distance of the hands between the origin and destination of the lift. D = V at destination - V at origin D is assumed to be at least 25 cm, and not greater than 175 cm. If the vertical travel distance is less than 25 cm, then D should be set to the minimum distance of 25 cm. TASK DATA OR TASK DATA OR VARIABLES VARIABLES Lifting Frequency (F) Asymmetric Angle (A) Average number of lifts per minute, as measured over a Asymmetry refers to a lift that 15 minute period.. begins or ends outside the mid -sagittal plane. * If the worker does not lift continuously for 15 A (see fig) defined as the angle minutes, special procedure are needed (see manuals) between the asymmetry line and the mid-sagittal line. Coupling (C) Coupling refers to the relationship between the hands and the object. C is classified as good, fair, or poor dependent on the A is not defined by foot position/torso twist angle, but nature and dimensions of the object and gripping by the location of the load relative to the worker's mid- method. sagittal plane. MULTIPLIERS DESIGN/REDESIGN USING THE RECOMMENDED WEIGHT LIMIT The multiplier values can be determined from Tables AND LIFTING INDEX Horizontal Multiplier (HM): Table 1. Vertical Multiplier (VM): Table 2. Distance Multiplier (DM): Table 3. Asymmetric Multiplier (AM): Table 4. Frequency Multiplier (FM): Table 5. RWL and LI can be used to guide ergonomic design: Lifting Duration classified as short , moderate and long duration (Table 6). Coupling Multiplier (CM): Table 7. 1) The individual multipliers can be used to identify specific job-related problems (multipliers magnitude indicates the relative contribution of each factor of the task) 2) RWL can be used to guide the redesign of existing manual lifting jobs or to design new manual lifting jobs. 3) LI can be used to estimate the relative magnitude of physical stress for a job.
    • LIMITATIONS Low back load The equation does not apply in the following situations 3D dynamic model are becoming as it could either under - or over-estimate the extent of more and more common for the physical stress associated with a particular lifting task : dynamic description of working - Lifting/lowering with one hand tasks. - Lifting/lowering for over 8 hours A combination of kinematics and - Lifting/lowering while seated or kneeling - Lifting/lowering in a restricted work space kinetic data is used (inversed dynamics) to compute - Lifting/lowering unstable objects. 1 Lbs = 4.44822162 N joints load in 3D. 1 inch = 2.54 cm - Lifting/lowering while carrying, pushing or pulling. - Lifting/lowering with wheelbarrows or shovels For the low back, the threshold - Lifting/lowering with high speed motion value for compression force in - Lifting/lowering with unreasonable foot/floor coupling the lower back should be below - Lifting/lowering in an unfavourable environment (ie. temperature and humidity) 3400 N (NIOSH). Low back load Low back load F = mg M=Fd Moment of muscles= ∑Moments of weights Hall 1999 Low back load Low back load Similar physical factors as the ones mentioned previously (heavy work, lifting, awkward position, vibration, stamina). Interaction between chronic Low-back load is estimated control low-back pain and via a biomechanical model muscle activity Evaluation of working during gait conditions Design of tools Arendt-Nielsen et al. 1996 Skotte et al. 2002 patient
    • Prevention of low back pain Take home messages Exercise to improve your posture, strengthen your back and improve flexibility, Lose weight, Avoid falls Stretching and strength training. Recommendations: - Definition Lift and bend properly. - Exposure response effect model * If an object is too heavy or awkward, get help. - Low back pain & low back load * Spread your feet apart to give a wide base of support. * Stand as close to the object you are lifting as possible. (revised NIOSH lifting equation) * Bend at your knees, not at your waist. * Tighten your stomach muscles as you lift the object up or lower it down. * Hold the object as close to your body as you can. * Lift using your leg muscles. * As you stand up with the object, DO NOT bend forward. * DO NOT twist while you are bending for the object, lifting it up, or carrying it.