Scientific Foundations: Ergonomics- Done Flashcards
Ergonomics is multidisciplinary, involving….
- Health professionals
- Engineers
- Behavioral scientists
- Physiologists
Ergonomics
Aka human factors
Refers to the study of the interaction between humans and their work
Literally means laws of work
Purpose of ergonomics
- To prevent acute and chronic injuries
- Make worksites comfortable
- Enhance productivity
- Reduce fatigue and errors
- Promise job satisfaction
—– can make jobs appropriate for workers of both sexes
Proper job design
Proper job design considers
- Size
- Strength
- Visual capacity
- Hearing capabilities
- Limitations
Ergonomics seeks to ———– rather than the ——–
Job to the person
Person to the job
Several —— disorders can be caused or aggravated by work-site factors
Musculoskeletal
Musculoskeletal disorders can affect the following tissue structures
- Muscles
- Tendons
- Ligaments
- Peripheral nerves
- Blood vessels
- Joints
- Cartilage
- Bones
Locations of musculoskeletal disorders
- Upper extremities
- Lower extremities
- Cervical spine
- Lower back
Common symptoms of musculoskeletal disorders
- Pain
- Swelling
- Erythema
- Numbness
- Paresthesia
Major worksite risk factors for work related musculoskeletal disorders if the upper extremities are…
- Repetition
- Force
- Mechanic stress
- Awkward postures
- Low temperatures
- Vibration
Avoiding and minimizing these risk factors is the goal in….
Task and tool design
Repetition
Refers to the performance of the same or similar tasks again and again
What constitutes a repetitive task?
- One work cycle lasts less than 30 seconds (a series of motions that is then repeated)
- For cycles lasting several minutes there are subcycles that constitute more than 50% of the overall cycle
Force is exerted in tasks that require..,
- Lifting weights
- Handling heavy tools
- Pinching with the fingers
- Applying other grips
The combination of repetition and force is particularly associated with
Carpal tunnel syndrome
Mechanical stress
Refers to the forces that result from a worker’s direct contact with work surfaces or tools
Examples of compressive forces
- Striking objects with hand held tools
2. Leaning against hard surfaces or corners of work tables
Compressive forces can lead to..,
Nerve compression disorders
Work frequently requires workers to assume ——– for prolonged periods of time or repetitive shorter periods
Awkward positions
Deviation from neutral position —– been identified as a risk factor for injury
Has
Deviation from neutral posture has been associated with the following types of injuries…
- Cervical spine injury
- Back injury
- Shoulder injury
- Forearm/elbow injury
- Wrist/hand injury
Main posture related mechanism of cervical spine injury
Extreme neck flexion and twisting
Main posture related mechanisms of back injury
- Twisting at waist
- Lifting with legs straight
- Bending and reaching repetitively
- Carrying, pulling, pushing or lifting heavy objects from below the knees or above the shoulders
- Lifting weight beyond one’s capabilities
Main posture related mechanisms of shoulder injury
- Raising the arm or elbow above midtorso without support
2. Reaching behind one’s body
Main posture related mechanism of forearm/elbow injury
Repeated rotation (ie supination and pronation)
Main posture related mechanisms of wrist/hand injury
- Repeated wrist flexion and extension
2. Holding the hand in ulnar deviation
Vibration caused by power tools or other work equipment can adversely affect…
The upper extremities
Whole body vibration can affect…
- Back
- Lower extremities
- Possibly shoulder and neck
Examples of workers exposed to whole body vibration
Drivers of trucks and heavy equipment
Cold environmental conditions may have an effect on
- Manual dexterity
2. Muscle strength
Cold environmental conditions may directly or indirectly cause…
Hand disorders
High risk jobs
- Office work
- Manual materials handling
- Assembly work
Office work presents ergonomic hazards that are associated with…
- Equipment
2. Overall working environment
Ergonomic hazards of computer work
May require individuals to assume static or awkward positions for typing if workstations are not properly adjusted
Other conditions in the office that can introduce hazards
- Poor lighting
- Obstructions in hallways
- Slippery floors
- Heavy objects
Examples of jobs that may entail manual materials handling
- Loading trucks
- Moving heavy goods
- Working in grocery stores
Types of movements that might be associated with manual materials lifting
Repeated….
- Bending
- Lifting
- Twisting
- Occasionally exposure to vibration
Risk for what type of injury is high with manual materials handling?
Back injury
Ergonomic hazards associated with assembly work
- often is machine paced
- repetitive motions
- sometimes performed in static or awkward positions
- sometimes performed with poorly designed tools
Methods that can be used to evaluate worksites for various ergonomic risks
- Interviews or questionnaires
- Observation and the use of a checklist
- Videotaping and analysis
Advantages of interviews or questionnaires
- Workers have the most complete view of their tasks throughout all work periods
- May reveal factors that might not otherwise be noted
Disadvantages of interviews or questionnaires
- High variability in the way workers report their perception of work performance
- Reports may be incomplete
- Reports may be biased
Interviews and questionnaires
Asks workers directly about their work
Advantages of observation and the use of checklists
- Observers using the same methods will look at all workers in the same way and thus introduce less variability
- Method is fairly efficient- one observer evaluates many workers in their work setting
Disadvantages of observation and use of checklists
- People may change the way they behave when they are under observation
- Limited time period for observation may cause some risk factors to be missed
- Observers must be trained to be consistent and accurate
Observation and use of checklists
Involves observing workers while they work and noting any risk factors
Advantages of videotaping and analysis
- Analysis is recorded and does not rely on one person’s assessment
- Tape can be repeated, slowed or frozen to evaluate details of work tasks
- Measurement of time and motion can be highly accurate
Disadvantages of videotaping and analysis
- Requires expensive equipment
- Requires experienced personnel
- Behavior may change during taping
- Only a small window of a workers time is recorded
- Not useful for evaluating highly variable tasks
Videotaping and analysis
Done by taping the worker on the job and later conducting a detailed analysis of motions and other risk factors
Some considerations and guidelines for analyzing or designing jobs are as follows:
- General environment
- Workstations and chairs
- Layout
- Postures
- Repetition
- Forces
- Mechanical stresses
- Vibration
- Lifting
- Work organization
General environment
- Provide adequate illumination
- Comfortable levels of temperature and humidity
- Good visibility of labels and signs
- Clear, audible auditory signals
Workstations and chairs
- These should be adjustable to accommodate workers of different sizes
Layout
- Place tools, controls and materials in front of the worker to prevent twisting, reaching and bending
- Keep work space free of obstacles
Postures
- Avoid static postures
2. Locate and orient work to promote neutral positions
Repetition
- Engineer the product or process to reduce repetition
- Vary tasks
- Rotate workers to different jobs
- Allow rest time
Forces
- Reduce the size and weight of objects held
- Use power grips rather than pinch grips
- Balance tools
- Provide correctly fitting gloves (not tight or bulky)
- Sharpen tools often
Mechanical stresses
- Ensure that handles on equipment fit the worker’s hands
2. Pad or eliminate sharp edges
Vibration
- Eliminate vibrating tools if possible
- Isolate sources of vibration
- Keep tools and equipment properly maintained
- Maintain even floor surfaces to reduce vibration from driving
- Reduce driving speeds of vehicles such as forklifts
Lifting
- Reduce size and weight of tools and objects that are lifted often
- Use mechanic lifting devices
- Use gravity to move work
- Raise the work (or lower the operator)
- Provide grips and handles
- Reduce friction where objects are slid from one point to another
- Increase friction where objects are held
- Evaluate lifting tasks according to NIOSH lifting guidelines
Work organization
- Staff adequately
- Alternate physically demanding and me tally demanding take to vary the rate and nature of tasks as much as possible
- Provide breaks (more-frequent short breaks are generally better thankless frequent long breaks)
