고려대학교 산업공학과 imen 368 인간공학 ii 10. anthropometry and work-space design...
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고려대학교 산업공학과
IMEN 368 인간공학 II
10. Anthropometry and Work-Space Design
Anthropometry – the study and measurement of human body dimensions HUMAN VARIABILITY AND STATISTICS
Human Variability Age Variability Sex Variability Racial and Ethnic Group Variability Occupational Variability Generational or Secular Variability Transient Diurnal Variability
Statistical Analysis Normal Distribution Percentiles
ANTHROPOMETRIC DATA Measurement Devices and Methods
height, breadth, depth, distance, circumference, curvature Civilian and Military Data
civilian -- out-dated and limited
고려대학교 산업공학과
IMEN 368 인간공학 II
Structural and Functional Data structural data (static data)
taken with the body in standard and still position functional data (dynamic data)
taken when the body adopts various working postures Use of Anthropometric Data in Design
1. determine the user population (the intended users)2. determine the relevant body dimensions3. determine the percentage of the population to be accommodated
design for extremes design for adjustable range design for the average
4. determine the percentile value of the selected anthropometric dimension lower-limit dimension – physical size of the system, not the human user upper-limit dimension
5. make necessary design modifications to the data from the anthropometric tables6. use mock-ups or simulators to test the design
고려대학교 산업공학과
IMEN 368 인간공학 II
GENERAL PRINCIPLES FOR WORK-SPACE DESIGN Clearance Requirement of the Largest users
lower-limit dimension, for the largest users (start with 95 %tile) Reach Requirement of the Smallest Users
upper-limit dimensions, for the smallest users (start with 5 %tile) reach envelop (area) – the 3D space in front of a person without leaning forward or stretching
Special Requirement of Maintenance People Adjustability Requirements
1. adjusting the workplace2. adjusting the worker position relative to the workplace3. adjusting the workpiece4. adjusting the tool
Visibility and Normal Line of Sight normal line of sight – the preferred direction of gaze when the eyes are at a resting condition about 10 to 15°below the horizontal plane
Component Arrangement increase overall movement efficiency and reduce total movement distance1. frequency of use principle2. importance principle
고려대학교 산업공학과
IMEN 368 인간공학 II
3. sequence of use principle4. consistency principle5. control-display compatibility principle of colocation6. clutter-avoidance principle7. functional grouping principle functional and sequence more critical than importance in positioning controls and displays subjective judgment, link analysis, optimization approach
DESIGN OF STANDING AND SEATED WORK AREAS Choice Between Standing and Seated Work Areas
standing frequent movements in a large work area heavy or large objects or exert large forces with their hands use of floor mats and shoes with cushioned soles
seated long-duration jobs allows for better controlled arm movements, provides a stronger sense of balance and
safety, improves blood circulation leg rooms or leg and knee clearance adjustable chairs and footrests
고려대학교 산업공학과
IMEN 368 인간공학 II
seat-stand Work Surface Heights
5-10 cm below elbow level for standing and at elbow level for seated – fig 10.9 Work Surface Depth
normal work area – a sweep of the forearm without extending the upper arm – fig. 10.10 maximum – a sweep of the arm by extending the arm from the shoulder
Work Surface Inclination slightly slanted surfaces (about 15°) for reading less trunk movement, less bending of the neck horizontal desk for writing
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
11. Biomechanics of Work awkward postures and heavy exertion forces – musculoskeletal problems low back pain and UECTDs
THE MUSCULOSKELETAL SYSTEM support and protect body and body parts, maintain posture and produce body movement, generate
heat and maintain body temperature Bones and Connective Tissues
protect internal organs – skull, rib cage support body movement and activities – long bones of the upper and lower-extremities Connective Tissues -- tendons, ligaments, cartilage, fascia joints -- synovial joints, fibrous joints (skull: fibrous tissues), cartilaginous joints (vertebral bones) no mobility joints, hinge joints, pivot joints, ball and socket joints
Muscles 400 muscles, 40 – 50% of BW supply energy and produce body motion generate heat and maintain body temperature muscle fibers, connective tissues and nerves a motor unit – “all-or-none” muscle contraction – concentric (isotonic), eccentric, isometric contraction no measuring device for tension in the muscle for muscle strength torque or moment static/dynamic muscle strength (isokinetic equipment, psychophysics)
고려대학교 산업공학과
IMEN 368 인간공학 II
BIOMECHANICAL MODELS musculoskeletal system as a system of mechanical links bones and muscles act as a series of levers Newton’s law Body segment not in motion – static equilibrium
The sum of all external forces on an object must be equal to zero The sum of all external moments on an object must be equal to zero
Single-Segment Planar, Static Model LOW-BACK PROBLEMS
Low-Back Biomechanics of Lifting the most vulnerable link because of most distant from the load L5/S1 normal range of strength capability of the erector spinal muscle at low back is 2,200 – 5,500N compression force on L5/S1
고려대학교 산업공학과
IMEN 368 인간공학 II
Seated Work and Chair Design LBP is common – loss of lordotic curvature in the spine increase in disc pressure lordosis and kyphosis seating – pelvis rotated backward lumbar lordosis into kyphosis backrest inclination angle – 110 to 120° lumbar support – a pad in the lumbar region – thickness of 5cm arm rest, tiltable seat surface
UPPER-EXTREMILTY CUMULATIVE TRAUMA DISORDER Common Forms of CTD
Tendon-Related CTD -- tendon pain, inflammation of tendon, tendonitits Neuritis – tingling and numbing Ischemia – tingling and numbing at the fingers Bursitis – inflammation of a bursa CTDs of the Fingers – vibration-induced white fingers (cold), trigger finger CTDs of the hand and wrist -- CTS (carpal tunnel syndrome) fig 11.7 CTDs at the elbow -- Tennis elbow (lateral epicondylitis), golfer’s elbow (medial epicondylitis) CTDs at the shoulder -- Rotator cuff irritation, swimmer’s shoulder, pitcher’s arm
고려대학교 산업공학과
IMEN 368 인간공학 II
Causes and prevention of CTDs Repetitive motion, excessive force application, unnatural posture, prolonged static exertion,
fast movement, vibration, cold environment, pressure of tools or sharp edges of soft tissues Non-occupational factors
Health condition, wrist size, pregnancy, use of oral contraceptives, sex, age, psychologi-cal factors
Prevention through administrative and engineering methods Worker education, training, appropriate work-rest schedule Redesign the workplaces and tools
Hand-tool Design1. Do not bend the wrist2. shape tool handles to assist grip3. provide adequate grip span (fig 11.9)4. provide finger and gloves clearances
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
(Q) Suppose a person is holding a load of 20-kg mass with hands in front of his body and his forearm are horizontal. The load is equally balanced the two hands
(A) W = mg = 20kg*9.8m/sec = 196NWon-each-hand = 98N
∑ Felbow = 0- 16N – 98N + Relbow = 0 Relbow = 114N
∑ Melbow = 0- 16N(0.18m) – 98N(0.36m) + Melbow = 0 Melbow = 38.16N-mshoulder
elbow
30°
BW = 78KgUpper arm = 0.028BWdistance from shoulder to elbow = 33cmcenter of gravity = 15 cm from the shoulder
HW:What are the reactive force and moment at shoulder?
고려대학교 산업공학과
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Cervical (7)
Thoracic (12)
Lumbar (5)
Sacrum
고려대학교 산업공학과
IMEN 368 인간공학 II
Clockwise rotational moment:Mload-to-torso (L5/S1) = Wload*h + Wtorso*b
Counterclockwise rotational moment:Mback-muscle = Fback-muscle * 5(N-m)
∑ ML5/S1 = 0Fmuscle * 5 = Wload*h + Wtorso*bFmuscle = Wload*h/5 + Wtorso*b/5
Torso weight = 350N, Load = 300N (about 30kg) thenFmuscle = 3,800N
Normal range of strength capability of the erector spinal muscle is 2,200 to 5,500N
Compression force on L5/S1
∑ F L5/S1 = 0Fcompression = Wload*cosα + Wtorso*cosα + Fmuscle
Suppose α = 55°, torso weight 350N, load = 450NFcompression = 450*cos 55° + 350*cos 55° + 5000 = 258 + 200 + 5000 = 5458N
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
고려대학교 산업공학과
IMEN 368 인간공학 II
12. Work Physiology
MUSCLE STRUCTURE AND METABOLISM Muscle Structure
primary function – generate force and produce movement smooth muscle – digestion of food and regulation of the internal environment – no conscious
control cardiac muscle – no conscious control skeletal muscle – the largest tissue in the body – 40% of body weight
direct conscious control, physical work possible muscle fibers>myofibrils>sarcomeres (fig 12.1) sarcomeres – myosin and actin the sliding filament theory of muscle contraction
Aerobic and Anaerobic Metabolism Phosphorylation – from ATP (adenosine triphosphate) and CP (creatine phosphate) to create
high energy phosphate compounds through aerobic and anaerobic metabolism (fig 12.2) AnaerobicA. Phosphagen (ATP - CP) System
1. ATP ADP + P + Energy 2. CP C + P + Energy (rebound ADP and P to ATP) most rapid means of replenishing
ATP in the muscle cell
고려대학교 산업공학과
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B. Anaerobic Glycolysis System – oxygen debt, not efficient1. Glucose (C6H12O6)n Lactic acid (2C3H6O3) + Energy2. Energy + 3ADP + 3P 3ATP
Aerobic Reaction – steady state1. C16H32O2 (carbohydrates and fatty acids) + 23O2 16CO2 + 16H2O + Energy2. 130 ADP + 130P + Energy 130ATP
THE CIRCULATORY AND RESPIRATORY SYSTEMS The Circulatory System
Transportation system of the body; it delivers oxygen and nutrients to the tissues and removes carbon diox-ide and waste products from the tissues
The Blood 8% of body weight red blood cells
transport oxygen and remove carbon dioxide formed in bone marrow and carries the Hb
white blood cells – fight germs and defend the body against infections platelets ( 혈소판 ) – stop bleeding Plasma – 90% water 10% nutrients and solutes
The Structure of the Cardiovascular Systems the heart – four-chambered (atrium and ventricle, atrioventricular valves) – fig 12.3 arteries and veins (one-way valves)
고려대학교 산업공학과
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the systemic circulation the left ventricle aorta arteries arterioles capillaries venules veins superior vena cava (inferior v.c.) the right atrium
the pulmonary circulation (oxygenation) the right ventricle pulmonary arteries to the lung arterioles capillaries venules veins pulmonary veins the left artium
Blood Flow and Distribution the resistance to flow – blood vessel’s radius and length systolic pressure – the maximum arterial pressure diastolic pressure – the minimum arterioles are the major source to blood flow cardiac output (Q) – the amount of blood pumped out of the left ventricle per minute
influenced by physiological, environmental, psychological, individual factors 5 L/min for rest to 25 L/min for heavy work to increase the cardiac output -- increase HR or stroke volume (SV) Q (L/min) = HR (beats/min) * SV (L/beat)
고려대학교 산업공학과
IMEN 368 인간공학 II
The Respiratory System Exchanges oxygen and carbon dioxide with the external environment The Structure of the Respiratory System
the nose, pharynx ( 인두 ), larynx ( 후두 ), trachea ( 기관 ), bronchi ( 기관지 ) lungs – alveoli (200 mil to 600 mil)
alveolar ventilation – the amount of gas exchange per min. in the alveoli the muscles of the chest, diaphragm
Lung Capacity total lung capacity (fig. 12.4) minute ventilation (volume) – tidal volume x frequency increasing the tidal volume is more efficient than increasing the breathing frequency
ENERGY COST OF WORK AND WORKLOAD ASSESSMENT Energy Cost of Work
basal metabolism – the lowest level of energy expenditure to maintain life; a resting person under dietary restrictions for several days and no food intake for 12 hours – 1600 to 1800 kcal/day or 1 kcal/kg/hour
2400 kcal/day for basal metabolism and leisure and low-intensity everyday nonworking activ-ities
Working metabolism (metabolic cost of work) – increase in metabolism from the resting to the working level
metabolic or energy expenditure rate during physical activity = working metabolism rate (metabolic cost of work) + basal metabolism rate – fig. 12.5
고려대학교 산업공학과
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physical demand of work Light – smaller than 2.5 kcal/min – oxidative metabolism Moderate – 2.5 to 5.0 kcal/min – oxidative metabolism Heavy – 5.0 to 7.5 kcal/min – only physically fit workers through oxidative metabolism, oxy-
gen deficit incurred at the start of work cannot be repaid until the end of the work very heavy ( 7.5 to 10 kcal/min), extremely heavy (greater than 10 kcal/min) – even physi-
cally fit workers cannot reach a steady state condition during the period of work – oxygen deficit and lactic acid accumulation
Measurement of Workload Physiological and subjective methods energy expenditure rate is linearly related to the oxygen consumption rate and to HR Oxygen Consumption
Energy expenditure rate (kcal/min) = 4.8 kcal/liter * oxygen consumption rate (l/min) Oxygen consumption = aerobic metabolism during work + anaerobic metabolism during re-
covery static work not well reflected in O2 measure
Heart Rate indirect measure of energy expenditure, not as reliable as O2 consumption rate resting HR – 60 to 80 beats/min increase from the resting to the steady state is a measure of physical workload max HR = 206 – (0.62*age) max HR = 220 – age
고려대학교 산업공학과
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Blood Pressure and Minute Ventilation BP -- not used as often as O2 consumption and HR but more accurate for awkward static
posture minute ventilation (minute volume) – the amount of air breathed out per minute – mea-
sured in conjunction with O2 consumption and used as an index of emotional stress Subjective Measurement of Workload
Borg RPE (Ratings of Perceived Exertion) Scale of 6 to 20 (beats/min) PHYSICAL WORK CAPACITY AND WHOLE-BODY FATIGUE
Short-Term and Long-Term Work Capacity Physical work capacity -- a person’s maximum rate of energy production during physical work the short-term maximum physical work capacity (MPWC) or aerobic capacity – VO2max – heart
cannot beat faster and the cardiovascular system cannot supply oxygen – 15kcal/min for healthy male and 10 kcal/min for healthy female
long-term maximum physical work capacity for continuous dynamic work, 5 kcal/min for male and 3.5 kcal/min for female
Causes and Control of Whole-Body Fatigue experienced whole-body fatigue around 30 to 40% of maximum aerobic capacity certainly feel fatigued if the energy cost exceeds 50% of the aerobic capacity because the body
cannot reach the “steady state”
고려대학교 산업공학과
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Causes of fatigue Accumulation of lactic acid in prolonged heavy work but not found with pro-longed moderate work; depletion of ATP and CP, symptom of disease or poor health
engineering methods to reduce the risk of whole-body fatigue – redesign the job and provide job aids
administrative methods(work-rest scheduling) without heat stress rest period = (PWC – Ejob)/(Erest – E job)
with heat stress Static Work and Local Muscle Fatigue
Static muscle contractions impede or even occlude blood flow to the working muscles Rohmert curve – the relationship between endurance and %MVC EMG and psychophysical scales Engineering and Administrative methods
고려대학교 산업공학과
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Figure 12.1 The structure of muscle
(the contractile unit of skeletal muscle)
고려대학교 산업공학과
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Figure 12.3 The anatomy of the circulatory and respiratory systems
Systemic circulation
Pulmonary circulation
고려대학교 산업공학과
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( 인두 )
( 후두 )
( 기관 )
( 기관지 )
( 횡경막 , 가로막 )
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Figure 12.4 Respiratory capacities and volumes
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Figure 12.5 The change in total energy expenditure rate as activity level changes
Resting-level metabolism
working metabolism
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BORG’S RATED PERCEIVED SCALE
6
7 VERY, VERY, LIGHT
8
9 VERY LIGHT
10
11 FAIRLY LIGHT
12
13 SOMEWHAT HARD
14
15 HARD
16
17 VERY HARD
18
19 VERY, VERY, HARD
20
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Figure 12.9 Relationship between static muscle endurance time and muscle exertion level