1. Assessment of Work Load and Pre-Employment Evaluation
Astrand pp
Jackson pp 53, 58-70
Gallagher and Moore pp

2. Assessment of Work Load in Relation to Work Capacity
Variability in capacity
Variability in response
Expression of workload by absolute VO2 alone is almost meaningless.
Should be a % of individual VO2 max

3. Assessment Maximal aerobic power Measure O2 uptake during work
direct - VO2 max test
estimation - predictive tests (HR)
Measure O2 uptake during work
portable devices, collect expired air
Measure HR during work
indirect
Fig 13-2, O2 uptake vs bike/work
depends on weight and fitness of a subject

4. Fig 13-3, Commercial fisherman
O2 uptake only represents work at the time the sample was collected
Subject often affected - test atypical
Test equipment may  HR, Ventilation
Continuous HR monitoring gives a good indication of the activity level for the day

5. Indirect Assessment Linear relationships between HR and VO2
HR may be used to estimate workload
Estimation of O2 consumption from HR may be inaccurate.
Continuously recorded HR
provides a comprehensive evaluation of circulatory strain imposed by workloads of varying intensity.
Fig fisherman
HR is a good estimation of work load when the work involves large muscle groups.
HR is higher in arm work than in leg work for the same work load (Fig 13-8).

6. Computer analysis of continuous HR data can generate mean values, peak values, distribution and heart rate variability.
Heart rate reserve (HRmax-HRrest)
Circulatory strain is best expressed as a percentage of an individuals HR reserve.

7. Assessment of the Organisms’ Response to the Total Stress of Work
The total stress imposed on the organism by a given work situation (physical or psychological) is generally reflected by a certain nervous and hormonal stimulation, more or less proportional to the degree of the stress.

8. Nervous Response Hormonal response  sympathetic stimulation -  HR
 by emotional and physical stress
may influence linear relationship
Hormonal response
total stress reflected by sympathetic response
measured with urinary excretion or ep and nor ep (blood samples)
Fig 13-9, Catecholamines  with standing, phsyical exertion, cold, emotional factors.  with duration and severity of muscular exertion.
Fig 13-9, there is considerable individual variation in catecholamine elimination under comparable stress situations.

9. Energy Expenditure Proper work/rest cycles for an 8 hour day.
Establish limits for permissible physical work loads.
The manner in which the work is performed is important.
Large individual differences in physical work capacity.
% VO2 max for 8 hour day is reasonable.
40% of max strength in repetitive muscular work.

10. Prolonged Work Classification
Physiological and psychological effects of a given energy output is influenced by:
individual VO2max
size of muscle being engaged
working position
type of activity (intermittent or continuous)
environmental conditions
Prolonged Work Classification
O2 uptake and HR (Table p 462)
Average person aged 20 to 30

11. Daily Energy Expenditure
Important for
calculation of energy needs
determine physical activity of groups
role of physical activity in health
Methodology
1) 24 hr recorded HR
2) time activity data
3) assessment of daily energy intake to maintain body weight
all fairly accurate +/- 15%

12. Wide individual variability in energy output
occupation
leisure activity
physical activity
environmental temp has a small effect (<4%)
daily rates 1300 to 5000kcal
regularly active male 2900kcal/day (Table 13-1)
regularly active female 2100kcal/day
Fig 13-11, Energy expenditure for different activities

13. Energy Expenditure Work expenditures
Most light work < 5 kcal/min (300 kcal/hr)
Some physical jobs kcal/min (600 kcal/hr)
Permissible limits for daily work kcal (300kcal/hr)
Limits are difficult due to individual differences in work capacity or fitness.
The individual will usually self regulate the rest pauses.
Peak load is more important than mean energy expenditure.
You can attain a higher8-hour energy expenditure if the work is consistent and does not have peak loads.
Basal Metabolic Rate: the rate of energy metabolism in a resting individual 14 to 18 hours after eating.

14. Energy Expenditure Recreational Activities
Different activities have different energy expenditures.
Cycling race 13 kcal/min (170lb or 77kg)
Golf kcal/min
Skiing uphill fast 21 kcal/min
Swim (fast crawl) 13 kcal/min
Running (5:30 pace) 22 kcal/min
Individual’s do activities at different intensities

15. Worker Strength Evaluation: Job Design and Worker Selection
Gallegher - Chapt. 21
Muscular strength is a very complex function that can vary greatly upon the methods of assessment.
Strength: capacity to produce a force or torque with a voluntary muscle contraction.
Measurement of human strength
We cannot directly measure force within a muscle.
Indirectly measure force at an interface between subject and a measurement device.
The cuff placement will influence the force measured.
Move cuff away from joint  force.

16. Types of Muscular Strength
Dynamic exertions
motion around the joint
different testing techniques
variable speed - difficult to compare
Isokinetic strength: strength throughout a range of motion at a constant velocity.
Isometric or Static exertions
no motion around the joint
force against a stationary load measuring device
use proper protocol (4 to 6 sec contraction, 30 sec to 2 min rest)
easy to quantify and compare - not representative of dynamic activity

17. Factors Affecting Strength
Gender
Age
Anthropometry
Psychological factors (Table 21.1)
Task influence
Posture (Fig 21.2 joint angle and force production)
Duration of exertion (Fig 21.3 Strength vs Endurance)
Velocity of contraction (Fig 21.4 Force - velocity curve)
Muscle Fatigue
Temperature and Humidity
 temp from 20 to 27oC  lifting capacity by 20%

18. Strength Measurement Strength Assessment for Job Design
Psychophysical methods
workers adjust demand to acceptable levels for specified conditions
provides ‘submax’ endurance estimate
Procedure
subject manipulates one variable-weight
two tests : start heavy and start light
add or remove weight to fair workload
without straining, becoming over tired, weakened, over heated or out of breath

19. Worker Selection and Placement
Used to ensure that worker can tolerate physical job.
Key principles
The strength test employed must be directly related to the work requirements.
Use of strength tests only to identify workers at risk of injury.
similar rates of overexertion injuries for strong and weaker

20. Isometric analysis (Fig 21.5)
for each joint there is a limit to the strength that can be produced
observe worker doing the task (video)
postures recreated using software
values compared to population norms - industrial workers
estimate % of population capable of this level of exertion
predict forces acting on lumbar spine

21. Isoinertial testing SAT - strength aptitude testing
air force standard testing
match strength of individual with job requirements
preselected mass - increase to max level
found incremental weight lifted to 1.83m - safe and reliable
PILE - progressive inertial lifting evaluation
lumbar and cervical lifts -progressive weight - variable termination
voluntary, 85 % max HR, 55-60% body weight
standards normalized for age, gender and body weight

22. Isokinetic testing
evaluates muscular strength throughout a range of motion and at constant velocity
humans do not move at constant velocity
isokinetic tests usually isolated joint movements
may not be reflective of performance ability
Attempts to redesign - multi joint simulation tasks for industry
whole body lifting strengths (Fig 21.8)
core stability required
still in progress, limited validity

23. Pre Employment Physical Evaluation
A. Jackson
Early pre-employment tests focused on cognitive abilities.
Physical ability tests have adverse impact on females.
potential legal review
federal civil rights legislation
documented differences in strength, VO2 max, % body fat
Employers must show that the pre-employment screening test measures only those abilities required to perform essential job functions.

24. INJURY RATES
Pre-employment tests are implemented to reduce work-related injuries.
Many occupations have a high incident of back injuries
80% of adults will experience a low back injury
back injuries caused by lifting, twisting, bending, pulling
3 Ergonomic approaches used to reduce industrial
back injuries.
Job redesign
Engineering approach to reduce exposure to risk factors
lower stacking heights, hydraulic lifts
biomechanical lifting model
define maximum permissible lifting limits

25. 3 Ergonomic Approaches con’t
Pre-employment testing
preferred ergonomic approach for physically demanding jobs that cannot be redesigned
select individuals with the capacity to safely perform job
strength testing
relationship between probability of injury and the percentage of capacity to perform the task
Training and education
train worker to lift properly
has not been successful
lifting pattern of individuals vary
lifting pattern affected by speed, size, shape

26. Fitness Fitness level appears to be 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 worksite exercise facilities
only 33% of these will train at the appropriate frequency, duration and intensity

27. Job Analysis
The goal of job analysis is to identify the important work behaviours demanded by the job.
Reduce job actions to words.
Essential component in developing pre-employment test.
Court cases regarding physical tests show the importance of job analysis.

28. Job Analysis Methods Can use a combination of the following:
Psychophysical (workers rate tasks)
RPE - rate of perceived exertion
.8 correlation - not biased by gender or experience
components: strength, CV endurance and movement quality
Physiological
CV components - O2, HR
Biomechanical methods
heights and weights of objects lifted
forces - opening, pulling, pushing
evaluate potential stress on lower spine

29. Validation Strategies
Determine accuracy with which test measures important work behaviors.
Validity depends on reliability and relevance.
Reliability: ability to differentiate among true levels of performance
Relevance: defining qualities being tested
Criterion related validity
data showing a significant correlation between pre-employment test and job performance

30. Content validity Construct validity
logical relationship between the pre-employment test and job requirements
the test represents the content of the job
Construct validity
establish that a construct is required for job success
the test measures that same construct
the degree to which a test measures an attribute that cannot be directly measured (coordination)
link important constructs and multiple indicators of job performance
tests theoretical and empirical relationships
relationship between physical ability and job constructs
FDNY physical ability test was found to discriminate against women as constructs were not related to the job

31. Physical Ability Test Selection
Content validation studies
Tests that simulate work tasks
Advantages
Simulate actual working conditions
fire fighter drags a dummy
lineman climbs a telephone pole
Disadvantages
safety (applicants are highly motivated)
do not measure maximal capacity

32. Motor ability and fitness test items
static strength (exert maximal force)
dynamic strength
balance
flexibility
Cut Score
the test score that an applicant must obtain to be considered for a job.
difficult to establish a cut score.
should you hire someone that just meets the minimal requirement?

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