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93 Cards in this Set

  • Front
  • Back
• What are 2 objective evaluation techniques?
o Physiology - Heart rate, oxygen consumption, electromyography
o Biomechanics - Applied forces, posture
• What are the subjective evaluation techniques?
o Body Assessment Map
o BORG Scale
o Checklist for analysis of workplace
o Rapid Upper Limb Assessment (RULA)
o Rapid Entire Body Assessment (REBA)
o Strain Index (SI)
o Quick Exposure Checklist (QEC)
• What is the purpose of the body map assessment?
o To subjectively determine aches and pains
• What is the purpose of the BORG scale?
o To subjectively determine perceived exertion or to rate workload
• How is the BORG scale used?
o Scale rating ranges from 6 to 20 with 6 having a Verbal Anchor of No Exertion At All and 20 having a verbal Anchor of Maximum Exertion. Users or workers are asked to verbally rate their perceived level of exertion using the Verbal Anchor Ratings
• What is the relationship between the BORG rating and heart rate?
o Typically the rating *10 = approx. current heart rate
• What does RULA stand for?
RULA: Rapid Upper Limb Assessment
• What does the RULA assessment help to identify?
RULA help identify contributors to Repetitive strain injuries (RSI's)
• What are the main contributors to Repetitive Strain Injuries (RSI's)?
o Postures of the Neck, Trunk, and Upper limbs (upper limbs = upper extremeties)
o Forces experienced by the body
o Muscle activities
• What does REBA stand for?
REBA: Rapid Entire Body Assessment
• What are the 3 types of postures that REBA is designed to evaluate?
o Dynamic
o Static
o Gross changes in position
• What types of information does REBA collect?
o Body postures
o Forces
o Type of movement or action
o Repetition
• What are the advantages to using REBA?
o Identify exposure to risk factors associated with MSD's and determine magnitude and severity of exposure
o Provide a postural analysis system that is sensitive to musculoskeletal risks in a variety of occupational tasks
o Provide a scoring system for muscle activity caused by the 3 types of postures
o Give an action level with an indication of urgency
• What does the Job Strain Index help to evaluate?
o Job's level of risk for developing MSD's in the:
 Hand, wrist forearm, and elbow
 Task variables, such as:
 Intensity of exertion
 Duration of exertion
 Hand/wrist postures
 Speed of work
 Duration of task per day
• What do the different SI scores mean?
o 0 - 3 = Jobs are probably safe
o 4 - 5 = Jobs associated with distal upper extremity disorders
o 7 - above = Jobs are probably hazardous
• What are the limitations of the Job Strain Index?
o Does not evaluate segmental vibration (doesn't predict risk of hand-arm vibration syndrome)
o Does not evaluate contact trauma (doesn't predict risk of hypothenar hammer syndrome)
o Limited to predicting the risk for distal upper extremity neuromusculoskeletal disorders
o 3 of the 6 (50%) task variables are subjectively evaluated by the analyst
o No mathematical relationship between the task variables
o Strain index tested on only 25 jobs in one industry
• What does QEC stand for?
QEC: Quick Evaluation Checklist
• What do the questions in the QEC help to evaluate?
o Postures
o Frequency of movement in the back, wrist/hand, shoulder/arm, and neck
• What do the questions in the QED help to assess/what are the advantages?
o Exposure to risks for work related MSD's
o Provides a basis for ergonomic interventions
o Assesses the 4 main body areas
o Involves both practitioners and workers in the assessment
• What are some of the areas assessed through questions in the Motion Economy Checklist? (for details, look at page 5 of the notes)
o Suboperations
o Holds
o Delays
o Movements
o Cycles
o Machine Time
• What are the 2 main types of questions asked about the areas?
o Can it be eliminated/shortened?
o Can it be made easier?
• What are some of the MSD's?
o Tendinitis
o Tenosynovitis
o bursitis
o Ganglionic cyst Tendinitis
o Carpal Tunnel Syndrome
o Vibration Syndrome
o Low back pain
• What are 3 types of controls or changes?
o Engineering Controls
 Equipment Design
 workstation design/redesign
 document holder, footrest, etc
o Administrative Controls
 training
 worker selection
 work pace/frequency
o Personal Protective Equipment (PPE) - Required
 safety glasses
 hard hats
 back belts and wrist splints are NOT PPE's
• When it comes to root cause analysis, what is the question to ask?
The question to ask in root cause analysis is: WHY?
(Human Problems vs. Workplace Solutions)
• What are the types of hand tools?
o Power tools (electrically powered)
o Hand tools (manually powered)
• What are the situational strength factors?
o Motivation, ego involvement
 will succeed or fear of injury
o Skill and experience
o Body motion, or lack thereof
o Ability to brace body against support structure
o Body posture
 Allowing use of strong muscles at advantageous leverage
o Body site used for exertion
 Eg. one foot or both feet, shoulder, hand or hands
o Coupling between body and object
• What are the individual strength factors?
o Age
o Gender
o Muscle cross section
o Length of muscle
o Speed of motion
 Static or dynamic exertion
o Fatigue
o Hand anthropometry
o Hand dominance
• Notes on Hand dominance?
o Majority of people are right-handed
o 10% of people are left-handed
 Most workstations and equipment is designed for right-handed users
o More natural feeling
• How does hand strength vary?
o Age
o Gender
o Exercise
 May be strengthened by use
 May be weakened by disuse
o Grip span
o Injury and/or disease
• What is the hand strength design guideline?
o If the force exerted continuously for a period of time -> Do not exceed 10-15% of maximum force
o If the force exerted over short duration or at frequent intervals -> Do not exceed 30% of maximum force
o If the force exerted occasionally & for a brief moment -> Do not exceed 60% of maximum force

o Apply caution while using these guideliens while designing for elderly individuals
o Insufficient information available about tolerance to force exertions (Imrhan, 1994)
• What are the types of grips? (see page 2 for pictures)
o Power Grip
 Fingers and sometimes thumbs are used to clamp
o Precision Grip
 Object is manipulated between fingers
 Thumb
 Pulp 2-5 (thumb with any other finger)
 Tip Pinch
 Key Pinch or lateral Pinch
 Chuck Pinch
• How can hand strength be measured?
o Hand dynamometer
o Pinch dynamometer
• What are the fundamentals of handle design?
o Force is exerted most effectively in compression rather than shear (what does shear mean?)
 Better to exert thrust perpendicular to handle axis
o Eliminate all pressure hot spots on gripping handle
 Finger shaping
 Unless designed with anthropometric factors
 The end of the toold
 Eg. End of pliers which may dig into the palm if handle is short
 Edges of raised surfaces
 Eg. Application of labels or logos
 Pinch points between moving points
o Shaping tool handle to provide high friction
 Gloves
 Be cautious with form fitting handles
o Facilitate secure holding & transfer of energy
 Provide mechanical interlocking between hand & handle
 Eg. Groves, bulges and serrations
o Maintain straight wrist
 Avoid overexertion of connective tissue
 Prevent compression of median nerve in carpal tunnel
 Bent wrist reduces the force that may be applied
 Bend the tool, not the wrist (Learning curve becomes an issue as people are not used to bend the tool)
o Force is exerted most effectively in compression not shear
o All sharp edges should be eliminated
 Finger shaping
 The end of the tool
 Edges of raised surfaces
 Pinch points
o If hand must fit in aperture? appropriate clearance should be provided
o Handle shape should reflect the curve of the hand
o Support surfaces at appropriate points
o Tools should be used equally for left and right hand users
o Use a power grip for tasks requiring force
o Power Grip
 Force line of action can vary with
 Force parallel to forarm (sawing)
 Force at an angle to forearm (hammering)
 Force acting on a moment arm (screwdriver)
 Used for power of holding heavy objects
 Inline grip vs. pistol grip (see page 3 for pictures)
o Pinch Grip
 Used for tasks requiring precision
 Used for control and precision
 Item held between distal ends of one or more fingers
• Notes on design guidelines?
o Avoid prolonged static muscle loading
o Perform twisting motions with elbows bent
o Maintain straight wrist
o Avoid tissue compression
o Avoid repetitive finger action
o Use the strongest working fingers
 Middle finger
 Thumb
o Design 1.5 in handle diameters for power grips
o Design a 3 in grip span for two-handled tools
o Decision grip surface to be compressible & nonconductive
o Keep the weight of the tool below 5 lbs
o Use gloves
o Use power tools such as nut & screwdrivers instead of manual tools
o Choose a power tool with the proper characteristics
o Use reaction bars & tool balancers for power tools
o Use the prove configuration & orientation of power tools
• How is information measured?
o Information is measured in bits.
• What is meant by bit?
o Bit is the amount of information needed to decide between 2 equally likely alternatives
 H = log2N
 H = Amount if information
 N = The # of equally likely alternatives
o If information is not weighted equally,
 H = Sum(pi*log2(1pi))
 P = Probability of the event
 i = alternatives from 1 to n
• What is band width?
o Band width is the maximum information processing speed of a given communication on channel
 Motor Processing Tasks 6-7 bits
 Speech communication 50 bits
• What is perception?
o Perception is the comparison of incoming stimulus information w/ stored knowledge to categorize information
• What is signal detection?
o Signal detection is determining whether a signal is present or not
• What are the different types of memory?
o Short-term memory
o Long-term memory
o Working memory
• What is the working memory? What is its capacity? How often does it decay?
o The working memory is a short term storage of memory
o The capacity of the working memory is approximately 7 +-2 items
o Working memory decays very quickly
• What are the recommendations for minimizing error for tasks requiring working memory?
o Minimize memory load
o Utilize chunks
 Eg. 12125551212 -> 1-212-555-1212
o Keep chunks small (less than 3 or 4 items)
o Keep numbers separate from letters
o Minimize confusion of similar-sounding items
 Eg. The number zero versus the letter "o"
• Can information in working memory be transferred to long term memory for later use?
o Yes, information in working memory can be transferred to long term memory for later use
• Notes on decision making and response selection?
o Humans are not optimal decision makers
o Humans have biases that influence outcomes:
 Limited amount of information used
 Undo weight is given to early cues
 Inattention is given to later cues
 Prominent cues are given greater weight
 A limited number of hypotheses are generated
 Small amount of responses are chosed
• What are they different types of attention?
o Focused attention (Eg. Assembler)
o Divided attention (Eg. Air traffic control)
o Sustained attention - Vigilance decremation with time
 More frequent rest
 Task variation
 Task feedback
 Appropriate levels of stimulation
• What does the identification of appropriate controls (coding methods) depend on?
o The identification of appropriate controls (coding methods) depend on:
 Detectability,
 Discriminability,
 Meaningfulness,
 Standardization, and
 Compatibility
• What do primary coding methods include?
o Shape
o Texture
o Size
o Location
o Operational Method
o Color
o Labels
• Explain the detectability of codes?
o A stimulus must be detected by human sensory mechanisms under the environmental conditions anticipated
 Eg. Color coded control knobs on underground mining equipment would not be detectable in low levels of light
• Explain the discriminability of codes?
o Every code symbol, even though detectable, must be discriminable from other codes symbols
 Eg. If 20 different levels of size are used to distinguish controls, it is highly likely that they will be confused
• Explain the meaningfulness of codes?
o Codes must be meaningful to the user (tribalism)
 Eg. Bent arrow on traffic sign means bend in the road ahead
• Explain the standardization of codes?
o When a coding system is to be used by different people in different situations, it is important that the codes be standardized & kept the same from situation to situation
 Eg. Red should mean the same on all signs (Red means danger)
• Explain the compatibility of codes?
o The compatibility of codes refers to the degree to which relationships are consistent human expectations
 Spatial, Movement are types of compatibility
• Regarding compatibility of control-machine movement, what should the direction of control movement be compatible with?
o The direction of control movement should be compatible with response movement of controlled machine
• Regarding control-effect relationships, how should the relationships between control action & resulting effects be?
o Relationships between control action & resulting effects should be made apparent through common sense, habitual use, similarity, proximity & grouping, coding, labeling, etc.
• Regarding shape coding of controls, what does the discrimination of shape-coded controls essentially involves?
o The discrimination of shape-coded controls essentially involves tactual sensitivity
• Regarding texture coding controls, can control devices vary in surface texture?
o Yes, control devices can vary in surface texture
• When determining the arrangement of the controls, what are some "operational rules" to keep in mind?
o Locate for the ease of operation
o Primary controls first
o Group related controls together
o Arrange for sequential operation
o Dead man control (a control that has a default setting that it reverts to automatically once you release it. ie. your steering wheel returns to a position that keeps you moving straight once you release the wheel)
o Feedback
o Guard against accidental activation
o pack tightly, but do no crowd
o be consistent
• When considering the location coding of controls what are some key things to keep in mind?
o For toggle switches, vertical arrangements are more accurate than horizontal
o The minimum distance between vertically arranged switches should be 2.5"
o The minimum distance between horizontally arrange switches should be 4"
• What is an operational method of coding? Give an example.
o Operational method of coding is when each control has its own unique method of operation. An example would be the windshield wipers in a car. Although every car has windshield wipers, the way they operate can vary greatly.
• What are the advantages and disadvantages to color coding of controls?
o Advantage - Colors can be picked that are meaningful (ie, red means stop and green means go)
o Disadvantage - The user must look at the control, in poor lighting colors are hard to detect, and dirt/wear may impede its effectiveness
• When considering labeling coding of controls...
o It should be the minimum coding requirement for any control
o It should not be used excessively, especially in environments when users are subject to quick speeds
• Redundant codes...
o Combine coding methods such as location, size and color, when it is unnecessary to use all 3.
• What are the types of displays?
o Dynamic displays
o Static displays
• How can information be classified?
o Quantitative (temperature, speed)
o Qualitative (direction, trend such as low or high)
o Status: limited conditions (on/off, stop/caution/go)
o Representational information (photos, maps, wastebasket for deleted files)
o Alphanumeric & symbolic information (signs, labels, braille)
o Time-phased information (Morse Code or blinking lights)
• What the display modalities?
o There are 5 display modalities (5 senses)
 Vision
 Hearing
 Touch
 Taste
 Smell
• Which display modalities or senses are the most popular?
o Vision
o Hearing
• Where is tactile generally used?
o Tactile is generally used in control design
• Give examples of how some display modalities are being used to warn or prevent people from danger?
o Odors used to warn homeowners of gas leaks
o Sour taste (medicine) to prevent children from accidentally swallowing it
• What needs to be considered to choose between a visual or an auditory display?
o Condition
o Purpose
• When are visual displays more appropriate?
o Environment is noisy
o Operator stays in place
o Message is long & complex and will be referred to later
o deals with spacial locations
• When are auditory displays more appropriate?
o Environment is dark
o Operator moves around
o Message is short and simple and requires immediate attention
o deals with events in time
• What is the range of frequency for auditory displays?
o 500 - 3000 Hz
• What does the frequency of the auditory display depend on?
o Use frequencies below 1000 Hz if signals need to travel long distances
o Use frequencies below 500 Hz if signals have to bend around objects
• How often do we need to use a modulated signal?
o 1 to 3 times per second
• To minimize the masking of signals, what can be done?
o Use signals with frequencies different than those that dominate any background noise
• What are the variables in design and selection of visual displays?
o Task-related considerations
 Consider the way each item on the display will be used and its importance
 Consider when the item on the display will be used
 Consider specific characteristics of users visual acuity and/or skill level
 Consider the use of same display during normal operation & emergency situations
o Type of display (based on the information the user needs to know)
o Information content & format
o Physical characteristics
• Give some recommendations of the locations of the displays?
o Within normal viewing area of an operator, with their surfaces perpendicular to the line of sight (line of sight = 0 +-15 degrees?)
o The more critical the display, the more centered it should be within the operator's cone of sight
o Avoid glare
o Group alignment
• What is the purpose of visual displays?
o Providing information either of a qualitative kind or providing exact quantitative information
• What are the different types of displays?
o There are 4 types of displays, they are:
 Moving pointer (fixed scale) example: spedometer (you should not have a moving scale with a moving pointer!!)
 Moving scale (fixed pointer) example compass or scale
 Counters
 Pictorial displays (Eg. seatbelt sign that turns on when the seat belt is not fastened)
• When are digital displays better than analog displays?
o A precise numeric value is required
o The values being read remain visible long enough to be read
• When are analog displays better than digital displays?
o Values are subject to frequent or continual change
o The direction of rate of change of the values is important
• Which of the followings is preferred: Moving point or fixed scale?
o Moving pointer
• What pattern should numerical increases follow?
o Numerical increases should match natural interpretation
 Eg. off, low, then high instead of low, off, high
• Should mix pointer scale indicators be mixed?
o No, mix pointer scale indicators must not be mixed
• What is the purpose of light signals?
o Indicating status of a system
o Alerting an inoperative system (or a part of the system) & indicating that action is required
• What are the common color coding systems?
o White
o Green
o Yellow
o Red
o Flashing red
• How does an alert start?
o An alert starts w/ an auditory warning signal accompanied by a flashing light
• When should alerts be used?
o To warn of an actual or potential dangerous situation
• How many warning lights should be used?
o Usually one
• Which type of alerts should be used: steady state or flashing?
o If event is continuous, use steady light
o If new conditions occur or emergencies, use flashing light
• What is the recommended flash rate?
o 3-10 per second (4 is best)
o If flash rates are to represent different levels of a variable then no more than 3 rates
• Where should the warning light be location?
o Within 30 degrees of operator's normal line of sight
• How about the warning light intensity or color?
o The light should be twice as bright as immediate background
o Red means danger (yellow means caution)
o With low to signal-to-background brightness contrast, red is best followed by green, yellow, & white.