Assessment of Physical Capacity and Job Demands

1
Job Analysis and Work Assessment

• CCW Readings
• P 58-74 Jackson
• Ch 14 - Louhevaara
• Ch 70 - Anderson
• Ch 72 - Key
• Ch 21 - Gallagher

2
Job Analysis A systematic evaluation of a task
with the purpose of generating information
which will ensure that human performance
requirements do not exceed human
capabilities (Kin 481 - A-K Arnold)
3
Outline

• Introduction - general outcomes and applications
• Job analysis
• Introduction
• Variables that influence performance
• methodology
• Applications (assessment)
• Fitness
• Job Placement Assessment (JPA)
• Functional Capacity Assessment (FCA)
• Validity of Job Analysis / Assessment

4
Job Analysis and Work Assessment

• It is important to know what we are demanding
  from an individual in a work (or sport) situation
• Ensure performance demands do not exceed
  capabilities
• Relates to
• Injury prevention
• Job performance
• Maintenance of work ability
• Information is utilized for
• Job redesign / ergonomic intervention
• Development of valid cutoff scores for Job
  Placement Assessment (JPA)
• Functional Capacity Assessment for return to work
  following injury (FCA)
• Detailed job analysis will provide us with the
  necessary information

5
Job Analysis

• Goal is to identify the important work behaviours
• Reduce job actions to words
• essential component in developing pre employment
  test
• JA utilizes a combination of approaches that
  include gathering
• Psychophysical data
• Biomechanical data
• and physiological data
• Methods may include
• Questionnaires, checklists and surveys
• interviews / Observations
• Video analysis
• Task simulations
• Measurements (weight, height, HR, VO2, distance,
  EMG)

6
(No Transcript)
7
Job Analysis - Methods

• Psychophysical
• Worker rates tasks on survey or performs
  simulations
• RPE - rate of perceived exertion - Borg or Likert
  scales
• Perception in terms of - CV demand, movement
  quality and strength (general / localized)
• Biomechanical methods
• heights and weights of objects lifted
• forces - opening, pulling, pushing
• evaluate potential stress on lower spine
• video or physical evaluations of simulations
• Physiological - CV components, blood analysis
• O2 use, HR, lactate, pH, hormone, ion,
  ATP, CP

8
BORG Scales
Old BORG RPE SCALE New BORG RPE SCALE HR Max VO2 max
6 7 8 Very,very light .5 Very,very weak
6 7 8 Very,very light 1 Very weak
9 10 Very light 2 weak
9 10 Very light 3 moderate
11 12 Fairly light 4 Somewhat strong 52-66 31-50
11 12 Fairly light 5 Strong 52-66 31-50
13 14 Somewhat hard 6 61-85 51-75
15 16 Hard 7 Very strong 86-91 76-85
15 16 Hard 8 86-91 76-85
17 18 Very Hard 9 92 85
19 20 Very,Very Hard 10 Very Very Strong
19 20 Very,Very Hard Maximal
9
Injury Rates

• Pre-employment tests are used to reduce work
  injuries
• some jobs - high low back injuries
• not serious but prevalent - 80
• lifting, twisting, bending, pulling
• 3 Ergonomic approaches to reduce back injuries
• job Redesign
• Engineering approach to reduce exposure to risk
  factors
• pre employment testing
• Preferred approach for physically demanding jobs
  that cannot be redesigned
• Select individuals with capacity to safely
  perform job
• Relationship between probability of injury and
  the of capacity to perform task
• education and training
• Train to lift properly - not successful

10
Job demands and Physical Fitness

• when redesign is not feasible, fitness becomes
  important
• secondary preventative measures
• individual health promotion
• healthy satisfying lifestyle
• maintaining work ability / healthy aging
• Fitness training / nutrition

11
Physical work load

• Affected by - of max strength used, frequency
  of peak loading, work/rest ratio, environmental
  factors, intensity
• level of strain depends on demand and individual
  capacity
• optimal / acceptable demand
• cardio, muscular and psychosocial strain
• physiological changes
• fatigue
• specific local changes (small muscles)
• if job demands
• do not exceed capacity - adaptation
• too high - fatigue, dec productivity
• prolonged / repetitive - damage / injury
• Muscular work at the proper intensity, frequency
  and duration will produce fitness training effects

12
Table 22.1 Louhevaara (2006 - not in CW)
13
Physical Fitness

• Fig 14-3 dimensions of Fitness
• CV capacity (aerobic, anaerobic)
• muscular performance
• motor coordination
• based on physiological demands and Anthropometric
  characteristics
• Utilization of capacity requires voluntary
  control - therefore all linked to MOTIVATION
• optimal situation - harmony between demand and
  fitness
• Situation is highly dynamic
• Text looks at specifics of Police, Fire and
  Professional Cleaners

14
(No Transcript)
15
Fitness and Injury

• Fitness level appears to be inversely related to
  injury
• High levels of aerobic fitness, strength and
  flexibility were inversely related to workers
  compensation costs of fire fighters
• Fitness programs should reduce musculoskeletal
  injuries
• Only 20-40 of employees will use work site
  exercise facilities
• Only 33 of these will train at the appropriate
  frequency, duration and intensity

16
Fitness and Productivity

• Physical exercise is one of the basic elements in
  maintenance of work ability
• linked with productivity, quality of work,
  absenteeism, and turnover rate
• Exercise programs must be tailored to job demands
• successful intervention requires
• commitment and support
• From both management and staff
• use of work time (for at least part)
• feedback and strong motivation
• positive experience with exercise
• skill full instruction
• confidential, voluntary and guilt free

17
Physical Ability Testing

• Ch 70 - Anderson
• Ergonomics - alter the demands of the job to
  match the worker-redesign
• Alternative approach is to match workers to the
  job, based on physical abilities
• decline of 20-40 in injury rates when physical
  ability testing is implemented
• Effectiveness depends on ability of test battery
  to assess what it intends
• requires
• thorough job analysis to identify and quantify
  essential aspects
• carefully chosen job placement tests - measure
  only tasks deemed essential by job analysis
• validation that tests predict performance on the
  job
• courts prefer testing to be focused on ability to
  perform not injury risk

18
Assessment

• Cost / Benefit of Testing
• cost of not being able to perform task
• probability of individual lacking ability
• Use normative data bases for different
  components.
• Use of standard protocols necessary
• balance with cost of testing applicants
• Would it be more cost effective to redesign job?

19
Assessment

• Test Battery Design
• test requires a high degree of relatedness to
  essential function
• Use realistic cutoff scores and normative data
• accurate - precisely measures attribute it says
  it measures
• reliable - yields same results
• over time and by different testers
• objective rather than subjective tests
• All applicants must be treated fairly
• all must be tested after same preparation and
  awareness
• same re-testing procedures

20
Assessment of Worker Capacities

• Workers compensation costs can be very high
• Knowledge of worker functional capacities
  important to reduce these costs
• Knowing workers capacity is important
• For decision to hire (JPA)
• For decision to return to work (FCA)
• Fig 72-1 - Key
• FCA- Functional Capacity Assessment
• return to work testing process
• individual physical functional work related
  capability
• confirmation of meeting or not meeting minimum
  physical requirements
• goal of FCA is return to work ASAP - even if
  limited capacity, some pain - may be modified
  tasks initially

21
(No Transcript)
22
Job Placement Assessment (JPA)

• Provides data prior to hiring
• assists managers - reduce injuries
• JPA - specific, objective, standardized protocols
  accurate and repeatable
• Identify employees capability for lifting,
  carrying, pushing, pulling
• Goal -accurately match worker with job
• Components of assessment fig 72-2
• weighted capabilities -CV, posture
• tolerance and endurance capabilities
• establish safe limits for work day
• Validity of participant - honesty
• fig 72-3 - less dishonest than generally assumed
  (5)
• utilize database correlation to confirm
• push vs pull, HR response at exertion

23
(No Transcript)
24
Worker Assessment Principles

• Principles for selecting FCA
• must contain standards for identifying validity
  of participation
• methodology must be consistent
• utilize standard equipment
• administrators must be trained and objective
• processing of results must be standardized
• Fig 72-5
• reports should compare results with demands of
  job
• unbiased and defendable decision about return to
  work

25
(No Transcript)
26
Outcomes

• FCA - dec re-injury rates
• decrease lapse of time before return to work
• decrease incidents and costs
• JPA - reduce injury and lost days
• eg fig 72-6 paper manufacturer
• pre and post JPA implementation

27
(No Transcript)
28
Validation Strategies

• Determine whether test actually measures
  important work behaviors
• Validity depends on reliability and relevance
• Reliability - ability to consistently
  differentiate among true levels of performance
• Relevance - ensure important qualities are being
  tested through job analysis
• Content validity
• Selection tests represents of job performance
• Relevance is clear and logical
• Often use work sample or simulation tasks
• Disadvantages - safety, often sub maximal

29
Validation Strategies

• Criterion related validity
• Criterion - standard of judgment
• Test successful people to determine what is
  required - use this to develop standards for
  success
• significant correlation between pre employment
  test and job performance
• Concurrent - correlates with important elements
  of job performance
• Predictive - significantly predicts future job
  performance
• Statistical validity
• prospective - test individual applicants - do
  not use results in hiring - analyze performance
  of all individuals hired
• productivity, retention, injury rate, evaluation
• Compare to assessment results
• Fig 70-1 - injury rate twice as high in those who
  failed screening test
• Or, implement test in hiring practice, and
  compare to those hired previously
• lack of control for other factors

30
(No Transcript)
31
Validation Strategies

• Construct Validity
• Establish that a construct is required for job
  success
• Use test that measures that same construct
• The degree to which a test measures an attribute
  that cannot be directly measure (coordination)
• link important constructs and multiple indicators
  of job performance
• Tests theoretical and empirical relationships
• Relationship between physical ability and job
• Eg, biceps used to lift box, test bicep strength
  using barbell, establish cutoff based on weight
  of boxes
• FDNY physical ability test was found to
  discriminate against women as constructs were not
  related to the job

32
Cut off scores

• Cut Score
• The test score that an applicant must obtain to
  be considered for a job
• Difficult to establish and justify
• See examples for firefighters at end of lecture
• Should they be relative to capacity, or absolute?
• Should someone be hired who just meets the
  minimal requirement?
• General Recommendations
• Cardiovascular - max of 40 of VO2 max for 8 hr
  day
• If peaks are higher, work / rest should be
  designed to keep average below 40
• Evaluate large number of subjects
• If 75 rate as acceptable workload, injury rate
  is decreased by 33
• Muscle work - Snook and Ciriello (1991)
• Table 21.2 (Gallagher)

33
(No Transcript)
34
Summary

• Employers are using pre-employment tests to
• enhance worker productivity
• to minimize the threat of litigation for
  discriminatory hiring practices
• and to reduce the risk of musculoskeletal
  injuries.
• The most common reason for ruling an employment
  practice invalid is the failure to show that the
  test measured important job behaviours.
• Proper job analysis will help ensure validity.

35
Muscular Function Assessment
Gallagher - OEH Ch 21(CCW)
36
Outline

• Muscle strength is a complex function that can
  vary with the methods of assessment
• Definitions and introduction
• Assessment methods
• Variables impacting performance

37
Muscle Function

• Gallagher
• Strength - capacity to produce a force or torque
  with a voluntary muscle contraction
• Power - Force distance time-1
• Endurance -ability to sustain low force
  requirements over extended period of time
• dynamic strength - motion around joint
• variable speed - difficult to compare
• static or isometric strength- no motion
• easy to quantify and compare
• not representative of dynamic activity
• Measurement of human strength
• Cannot be measured directly
• interface between subject and device influences
  measurement
• Fig 21.1 Biomechanical eg.
• Q (F a)/b or c or d
• force from muscle is always the same
• results are specific to circumstances

38
(No Transcript)
39
Factors Affecting Strength

• Gender
• Age
• Anthropometry
• Psychological factors - motivation
• table 21.1

40
Factors Affecting Strength

• Task influence
• Posture
• fig 21.2 - angle and force production
• Duration - Fig 21.3
• Velocity of Contraction - Fig 21.4
• Muscle Fatigue
• Static vs dynamic contractions
• Frequency and work / rest ratio
• Temperature and Humidity
• inc from 20-27 C - decrease of 10-20 in muscle
  capacity

41
(No Transcript)
42
(No Transcript)
43
(No Transcript)
44
Strength Testing (intro)

• Isometric strength testing
• standardized procedures
• 4-6 sec contraction, 30-120 sec rest
• standardized instruction
• posture, supports, restraint systems, and
  environmental factors
• worldwide acceptance and adoption
• Dynamic strength
• isoinertial (isotonic)- mass properties of an
  object are held constant
• Psychophysical - subject estimate of (submax)
  load - under set conditions
• isokinetic strength
• through ROM at constant velocity - no
  acceleration or deceleration
• Uniform position on F / V curve
• Standardized
• Isolated muscle groups
• Research and rehabilitation

45
Strength Testing

• Testing for worker selection and placement
• Used to ensure that worker can tolerate physical
  aspects of job
• similar rates of overexertion injuries for
  stronger and weaker workers
• Key principles
• Strength test employed must be directly related
  to work requirements
• must be tied to biomechanical analysis
• Isometric analysis fig 21.5
• for each task - posture of torso and extremities
  is documented (video)
• recreate postures using software
• Free body diagrams (Kin 201)
• values compared to pop. norms
• industrial workers
• estimate capable of level of exertion
• predict stress on lumbar spine

46
(No Transcript)
47
Isometric Considerations

• Discomfort and fatigue in isometrics thought to
  result from ischemia
• Increasing force, increases intramuscular
  pressure which approaches then exceeds perfusion
  pressure - lowering then stopping blood flow
• Partial occlusion begins at 20-25 MVC
• Complete occlusion above 50 MVC
• Fig 15-19 Astrand
• Max hold time affected by MVC
• Recommend less than 15 for long term
  requirements
• Fig 15-20 Astrand
• With repeated isometric contractions Force and
  Frequency influence endurance
• Optimal work / rest ratio of 1/2
• Duration important as well (Astrand - blood flow)

48
(No Transcript)
49
Isoinertial Testing

• Consider - biomechanics and grip
• Stabilization requirements
• justification of cut off scores
• Examples from industry
• SAT - strength aptitude testing
• air force standard testing
• Pre-selected mass - increase to criterion level -
  success or failure
• found incremental weight lifted to 1.83m to be
  best test as well as safe and reliable
• PILE - progressive inertial lifting evaluation
• lumbar and cervical lifts -progressive weight - 4
  lifts / 20 seconds
• standards normalized for age, gender and body
  weight
• variable termination criteria
• voluntary, 85 max HR, 55-60 body weight

50
Psychophysical testing

• psychophysical methods
• workers adjust demand to acceptable levels for
  conditions
• provides submax endurance estimate
• Procedure -
• subject manipulate one variable-weight
• Either test starting heavy or light
• add / remove weight to fair workload
• Fair defined as without straining, becoming
  over tired, weakened, over heated or out of
  breath
• Study must use large numbers of subjects
• evaluate/design jobs within capacities of workers
• 75 of workers should rate as acceptable
• If demand is over this acceptance level 3 times
  the injury rate observed to occur

51
Psychophysical (cont)

• Summary
• Table 21.2 (Snook and Cirello) (see slide 32)
• Advantages
• realistic simulation of industrial tasks
• very reproducible - related to incidence of low
  back injury
• Disadvantages
• results can exceed safe as determined through
  other methodology
• biomechanical, physiological

52
Fire Fighters

• 200 subjects - asked about job demands of
  physical fitness and aerobic power, muscular
  performance and motor coordination
• smoke diving with SCBA- highest aerobic demand
• clearing passages with heavy manual tools -most
  muscular demand
• roof operations- highest motor control demand
• Aerobic Power Demand then assessed- Table 14-1
• often 2.1-2.8 L/min
• max frequent 3.8 L/min 180 bpm
• compounded by
• need to disperse heat
• no possibility of alleviating load
• recommend minimum of 34-45 ml/min/Kg for VO2max

53
(No Transcript)
54
(No Transcript)
55
Fire Fighters

• Muscular Performance
• biomechanical factors - simulated clearing task -
  9 kg power saw - floor to ceiling
• high compression on L5/S1
• 90 of isokinetic strength
• back and knee extensors
• Table 14.1 - determined that a minimum of good or
  excellent is needed for muscular performance
  measures
• Bench press
• Sit up
• Squat
• Pull up