Ergonomics

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Ergonomics

• The science of fitting the job to the worker

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MULTIDISCIPLINARY NATURE OF ERGONOMICS

• Anatomy and physiology
• Engineering Psychology
• Engineering
• Medicine
• Anthropology
• Biomechanics

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Benefits of Ergonomics

• Decreased injury risk
• Increased productivity
• Decreased mistakes/rework
• Increased efficiency

• Decreased lost work days
• Decreased turnover
• Improved morale

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HISTORICAL PERSPECTIVE
Ramazzinni described posture and disease in
1700s Before WWI labor surplus During WWII labor
scarce WWII mass production of sophisticated
equipment Reading Errors Control-Display
Relations
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EROGONOMIC CONCEPTS
Tool design Workstation Design Material
handling limits Visual and auditory task design
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ENVIRONMENTAL FACTORS
Noise Vision Thermal Chemical
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PSYCHOLOGICAL STRESS

• Machine Pacing
• Shift Work
• Morale

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PHYSICAL

• Posture
• Force
• Repetition
• Manual Materials Handling

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TARGET REGIONS

• Back
• Upper Extremities
• Lower Extremities

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DESIGN AND DISEASE
POSTURE DISCOMFORT
Standing Legs, Feet, Back
Sitting Neck, Back, Shoulders
Reaching Shoulders, Upper Arms
Head Bent Back Cervical Region
Trunk Bent Forward Lumbar Region
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STATIC EXERTIONS

• Holding activities
• Carrying
• Standing
• Pushing and pulling
• Arms raised

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EFFECTS OF STATIC EXERTION
When effort greater than or equal to 60 percent
MVC blood flow almost completely
interrupted. 15-20 percent MVC blood flow just
about normal but still is associated with
pain. MVC less than or equal to eight percent can
probably be maintained indefinitely.
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WORKSTATION GUIDELINES
Reduce static component and allow worker to use
optimal posture Optimal posture usually at
midpoint of limbs range of motion Avoid muscular
insufficiency Avoid forward reaches in excess of
16 Elbows down close to the body flexor angle
around 90 degrees
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WORKSTATION GUIDELINES (continued)
Sit-Stand preferred but rarely seen Use gravity
do not work against it Avoid the need for
excessive head movement Avoid compression
Ischemia
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WORKPLACE INDICATORS

• Performance deteriorationEngineering
• Quality Control problems
• Absenteeism and turn-overHuman Resources
• Musculoskeletal disordersOSHA Logs WC reports
• Complaints of fatigue and discomfort

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NIOSH LITERATURE SURVEY (NIOSH 97-141)
In 1994 32 of LWD cases (705,800) were result of
overexertion or repetitive motion 367,424
Lifting 65 affected back 93,325 pushing/pulling
(52) 68,992 holding/carrying (58) 92,576
repetitive motion, 55 wrist 83,483 NEC
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GROWING AWARENESS OF CTDs
Year Number of Repeated Trauma Cases Number of Repeated Trauma Cases Total Number of Illnesses
1980 23,200 (18) 130,200
1981 23,000 (18) 126,100
1982 22,600 (21) 105,600
1983 26,700 (25) 106,100
1984 34,700 (28) 124,600
1985 37,000 (30) 125,400
1986 45,500 (33) 136,800
1987 72,900 (38) 190,200
1988 115,400 (48) 240,900
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TOP FIVE CTD INCIDENCE INDUSTRIES BY RATE1990
Meatpacking Poultry Processing Household
Refrigerator/Freezer Motor Vehicle and Car
Body Mens and Boys Trousers and Slacks
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TOP FIVE CTD INCIDENCE INDUSTRY CLASSES BY
NUMBER1990
Meat Products Motor Vehicles Mens and Boys
Furnishings Miscellaneous Plastic
Products Aircraft and Parts
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Types of Injuries

• Muscle pain
• Joint pain
• Swelling
• Numbness
• Restricted motion
• Repetitive stress injury

• Repetitive motion injury
• Cumulative trauma disorder
• Musculoskeletal disorder

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CUMULATIVE TRAUMA DISORDERS
A class of musculoskeletal disorders arising from
repeated biomechanical stress due to ergonomic
hazards. Common names for these disorders are

• Carpal Tunnel Syndrome
• Tendinitis
• Tenosynovitis
• Ganglion cyst
• Tennis Elbow

• Trigger Finger
• DeQuervians Disease
• Thoracic Outlet Syndrome
• Bursitis
• Synovitis

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Ergonomic Risk Factors

• Repetition
• Awkward posture
• Forceful exertion
• Static posture

• Mechanical contact stress
• Temperature
• Vibration

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PSYCHOSOCIAL FACTORS
LA Times HETA 90-013-2277 NIOSH PUBS
1-800-356-4674 US West HETA 89-299-2230
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PSYCHOSOCIAL FACTORS(continued)
Significant Findings Fear of being replaced by
computers Enlarged Jobs Uncertainty
about job future Work pressure Lack of
co-worker support Lack of productivity
standard Lack of participation in
decision-making Perception management not value
ergo
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Ergonomic Controls

• Engineering
• Administrative
• Work Practices

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CONTROL TECHNOLOGY

• Tool redesign
• Workstation redesign
• Job methods
• Early detection
• Job rotation
• Machine pacing
• Medical surveillance

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REDUCTION OF REPETITION
Task Enlargement Mechanization Automation
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REDUCTION OF EXTREME JOINT MOVEMENT
Altering tool or controls Workstation
Design Moving the Worker
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REDUCTION OF FORCE
Reducing the force Spreading the force Better
mechanical advantage
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ADMINISTRATIVE CONTROLS HAZARD PREVENTION AND
CONTROL

• Rest-pause
• Increase number of employees
• Job rotation
• Physical conditioning
• Relief personnel
• Medical management

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MATERIALS HANDLING
Lifting/Lowering Pushing/Pulling Carrying Weights
and Forces Frequency of activities Load Center of
Gravity
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JOB RISK FACTORS
Weight lifted Position of load center of
gravity Frequency Posture Torso
Flexion Twisting Arms extended
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JOB DESIGN
Can reduce one-third of compensable LBP Minimize
reach and lift distances Keep off floor Work
station design Frequency Relax time
standard Rotation Work-Rest allowances
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JOB DESIGN (continued)
Minimize Weight Mechanical aids Carton
capacity Balance contents Convert Carry to
push/pull Push over pull Use large wheels
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TRAINING
Focus on awareness and avoidance Get object as
close to body as possible Planning Use of
handling aids Back Schools Strength and fitness
important
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WORKPLACE USE OF BACK BELTSNIOSH 94-122

• Insufficient Data that belts significantly reduce
  trunk loading
• Insufficient data that wearing reduces risk of
  injury based on IAP and EMG
• May strain cardiovascular system
• Insufficient data that discontinuation of use
  increases risk among healthy workers

NIOSH does not recommend as tool for prevention
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ORGANIZATIONAL INFLUENCES
Wage Systems Quality Control Management-Labor
Relations Machine-paced versus Self-paced
work Rest Breaks Overtime Shift Work
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RECOMMENDATIONS

• 1. Identify Team Members
• 2. Identify problem jobs
• 3. Survey Employees
• 4. Develop Plan of Action
• 5. Select most feasible
• 6. Implement on small scale
• 7. Train
• 8. Measure response
• 9. Wider application or goto 4
• 10. Goto 2

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REDESIGN EFFORT
Based on job analysis Employee
Feedback Anthropometry Fitting Trials
(Prototyping) Monitoring and Measurement
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REMEMBER WORKSTATION DESIGN GUIDELINES
Design where hands spend most of time Normal
reach envelope Elbow height Edge
compression Limit forward reaches to 16!
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WORK SITE ANALYSIS

• Review OSHA 200 log
• Employee interviews
• Performance Data (turnover, etc.)
• Video analysis of identified hazardous positions

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Ergonomics Program Elements

• Management leadership and employee participation
• Hazard information and reporting

• Job hazard analysis and control
• Training
• MSD management
• Program evaluation

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REFERENCES
Applications guide for the revised NIOSH lifting
equation NTIS PB94-176930 (703)
487-4650 12.00 NTIS PB91-226274 Scientific
Documentation Elements of Ergonomic
Programs NIOSH 97-117 1-800-35-NIOSH Musculoskelet
al Disorders and Workplace Factors NIOSH
97-141 Work Practices Guide for Manual
Lifting NIOSH 81-122
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REFERENCES (continued)
Cumulative Trauma Disorders A Manual for MSDs of
the Upper Limbs, Putz-Anderson Fitting the Task
to the Man, Grandjean Taylor and
Francis 1-800-821-8312 Methodological
Limitations in the Study of VDT use and
UEMDs Gerr, Marcus, Ortiz, American J. Ind. Med.
29649-656 (1996) Ergonomics The Study of Work,
OSHA 3125,www.OSHA.gov Dan Ortiz, Georgia
Tech [phone] www.oshainfo.gatech.edu