STRENGTH TESTING IN SCHOOL DISTRICTS
The need for physical
testing for workers in manual materials handling jobs has been
recognized by risk
managers, personnel specialists, physiologists, occupational physicians
and ergonomists increasingly over
the past decade. Each of these groups have independently come to
recognize the benefits to both the
individuals being tested and the organizations themselves. Risk
managers have an interest in job safety and
reducing workers' compensation costs. Personnel specialists seek to
hire the most qualified individual
available, reduce absenteeism and sick leave, and yet comply with state
and federal EEO mandates.
Physiologists and physicians seek to reduce unnecessary injuries and
find ways to better predict in advance
those most likely to become injured. Ergonomists seek to study
individual jobs and find ways through either
job redesign or job selection systems that can better match the worker
to the work.
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Cognizant of these
issues, MED-TOX Health Services has developed a
model approach to assist school
districts in the use of validated strength tests for new hires.
Over-exertion Injuries and School District Employees
Overexertion and falls account for more than $25 billion in workers
compensation costs each year, according to Liberty Mutual Research
Institute for Safety’s 2014 Workplace Safety Index. The top 10
causes to workplace injury are:
1. Overexertion $15.1B 25.3%
2. Falls on same level $9.19B 15.4%
3. Struck by object or equipment $5.3B 8.9%
4. Falls to lower level $5.12B 8.6%
5. Other exertions or bodily reactions $4.27B 7.2%
6. Roadway incidents involving motorized land vehicle $3.18B 5.3%
7. Slip or trip without fall $2.17B 3.6%
8. Caught in/compressed by equipment or objects $2.1B 3.5%
9. Repetitive motions involving micro-tasks $1.84B 3.1%
10. Struck against object or equipment $1.76B 2.9%
from 2004 reveal that police officers have the highest injury rates of
any public sector
occupation. Ranking second are custodians, followed by firefighters.
Ranking 4th, 5th, 6th, and 7th, and 8th
are building maintenance workers, teaching assistants, bus drivers, and
grounds maintenance workers.
With the exception of firefighters, all of these occupational groups
are employed by school districts.
The largest single
category of lost work time was caused by over-exertion injures,
especially those that
involve lifting. Back and spine injuries were the most frequently
injured body parts, accounting for a quarter
of the total cases (Department of Industrial Relations, 2004). Clearly,
school district personnel have an
interest in reducing injury rates among their workers since they are
clustered at the top of the most frequently
injured public sector workers in the state.
In addition, according
to national statistics, occupations that involve the lifting and
carrying of disabled individuals also have a very high rate of
These workers have duties similar to Special Education
Workers who must lift and move disabled students several times over the
course of the school day.
over-exertion is described as the cause of lower back pain
by over 60 percent of the people
suffering from it. If the over-exertion injury involved low-back pain
with significant lost time, less than one-third
of the patients ever return to their jobs (Chaffin & Andersson,
Caused by Over-exertion
injuries account for a significant number of all work-related back
injuries to school
district employee, it makes sense to reduce its potential. Hiring
workers with the adequate
strength to perform the job is one way of reducing these injuries. Any
approach to strength testing must
meet two goals:
- Provide a valid and
legally defensible job analysis of the essential, frequently performed,
physically demanding tasks associated with the occupation.
- Provide a physical
ability test that is job-related, valid and reliable that can
confidently be used in
the selection of individuals for physically demanding jobs.
Strength tests must be
chosen on the basis of safety, reliability, and validity. Validity and
discussed below. Ability tests are safer than work sample tests because
it is preferred to determine how
much weight an applicant can lift rather than asking the applicant to
lift a heavy weight. If the applicant
does not have the necessary strength to lift the weight an injury may
occur during the test. Using an ability
test allows the district to determine whether the applicant can only
lift 10 lbs. or 100 lbs. safely.
Strength tests must be designed to ensure that the ability test
(selection device) is empirically demonstrated
to be related to the job (APA, 1999; SIOP, 2003).
ability tests can be subjected to a high standard of legal and
administrative review, empirical evidence is usually necessary to show
A high standard of evidence is also necessary since all tests of
strength show adverse impact against females
(Biddle, 2005). The Uniform
Guidelines on Employee Selection Procedures
state that validity evidence is
necessary when a given test has an adverse impact on a protected group
(EEOC, 1978). Validity evidence
typically consists of a sound quantitative job analysis and the
empirical linkage of the test to critical tasks
measured during the job analysis.
To demonstrate job
relatedness, it is necessary collect job information from experienced
workers. The job
analysis inquiry is directed at collecting tasks from incumbents which
require muscular strength. Muscular
strength involves the continuous exertion of maximum muscle force for a
brief period time. Tasks that
involve the lifting, pulling, pushing or carrying of objects and
materials require muscular strength.
group interview, workers and the MED-TOX representative go to
storerooms, school sites and other work areas to directly examine
tools, equipment and materials that had
been described by workers during the meeting. An industrial scale
and/or force gauge are used to directly
weigh as many of the relevant objects as needed. If additional
materials or tools are found that are also
lifted, these objects are weighed, the weights recorded, and the
lifting tasks added to the task is produced for
In order to measure a
job, one needs a measuring tool. Rating scales are the most useful
when performing job analysis activities with task inventories. Rating
scales can have a number of
customized features depending on the job and specific organizational
needs. To validate a strength test,
however, it is important to elicit from workers:
Whether or not the
task is performed?
How physically demanding is the task?
How far the object is carried?
How often the task is performed?
How important the task is to the job?
What is the relationship between accuracy and efficiency and job
Workers' complete the
task inventory. Employee ratings are then statistically examined to
most critical and physically demanding tasks.
which strength tasks are critical for the job, it is next necessary to
determine which tasks
are suitable for utilization as work samples. Ideally, the tasks
selected should be among the most demanding
tasks workers are expected to perform. Additionally, other criteria
should be considered including:
- Safety to incumbents.
Tasks selected should be safe to perform in a testing situation. Some
might not be dangerous to experienced workers, but could be to a novice.
- Reasonable time to
administer. The tasks selected for work sample development should be
which can be completed in a reasonable amount of time.
- Unambiguous scoring
and clarity of results. Tasks selected should be amiable to an
scoring or rating system. There should be no disagreement as to what
constituted various levels of
- Subjective ratings on
"style of lifting" or "ease of lifting" are less suitable when
objective measures are possible.
- The tasks
selected should be as simple as possible from both the point of view of
instruction to incumbents and administration of the work sample.
- Independence from
training and experience. The tasks selected should be dependent upon
and not "tricks of the trade" for success. Novice and experienced
individuals with the same level of
strength should have the same score.
- Commonality. The tasks
selected should be commonly performed by as many workers as possible.
Critical tasks that
meet the criteria can be categorized in a variety of ways. For example,
all tasks involving
the use of a wheelbarrow might form a group or task set. Alternatively,
all tasks that involve work at
particular work site, or all tasks performed while repairing heavy
equipment could form other sets. The
nature of the job and tasks performed typically lend themselves to the
selection of appropriate task sets.
These sets are
important because they help organize the work and ensure
that a variety of lifting tasks can be
used to construct work samples. An example of a task set might be:
Five Gallon Container
(Paint, Joint Compound, Floor Sealer) Tasks
1. Lift/carry a five
gallon can of floor sealer (approx. weight 46.3 lbs. ).
2. Carry a five-gallon
bucket of paint (55.4l bs.).
3. Stack a shipment of
joint compound (51 lbs.) that has been delivered.
4. Lift a five gallon
bucket of paint into the back of a vehicle (55. 4 lbs.).
5. Lift a five-gallon
bucket of paint up onto a stack of other five-gallon paint buckets
Work samples may then
be developed from this set of common critical tasks such as:
Five-Gallon Bucket Stack
Approach a row of four
numbered five-gallon buckets of material. Stack the #3 buck on top
of bucket #4 and then stack bucket #2 of bucket #3. Next take bucket #1
and place it on top
of bucket #2. Immediately take bucket #1 to a truck bed 15 feet away
and set it down.
Immediately pick it up and carry it back to its original starting
location. Repeat this process
with bucket #2 and bucket #3. When bucket #3 has been set on the
ground, all the buckets
are in their original starting position. Bucket #4 never moves.
In our studies this
job simulation has worked particularly well. The correlation
performance on this work sample and measured strength is .50. Other
work samples used for school district
workers have included lifting a bus battery (r = .66), holding a bus
starter (r = .79), loading building
materials into a wheelbarrow and transporting it a short distance (r =
.63), and evacuating a child off a bus
(r = .71). In all, MED-TOX has validated physical ability tests for the
following school district occupations:
- Bus Drivers
- Warehouse Workers
- Bus Equipment Mechanics
- Grounds Maintenance
- Building Maintenance
- Food Service Workers
Appropriate Static Strength Tests
MED-TOX has used the
Jackson Strength Evaluation System (JSES) in several projects with many
districts and has found it to be a valid and reliable predictor of the
ability to perform lifting, pushing, pulling,
and carrying tasks.
The JSES has three
qualities that make it ideal for employment testing. It has been shown
to be safe, reliable
(r = . 97), and practical. Results are obtainable within 15 minutes.
The JSES is widely recognized as a
reliable and valid indicator of the amount of muscular strength
possessed by individuals. At the present time
many industrial medical clinics and employers are obtaining the JSES.
The test is relatively inexpensive (it
can be obtained for less than $5,000), it is practical, safe and
portable. More than 86,000 California school
district job applicants have already been tested for employment using
Field Testing and
A sample of
experienced workers is typically chosen for test validation. The sample
should consist of
individuals from various ages, racial groups and both genders. Of
course, many organizations will not have
a significant number of females for testing nor will they have
individuals employed who cannot perform the
job. Without representatives from these groups, it is more difficult to
set a defensible cut-off score.
of the JSES is assessed
by comparing the scores of the two recorded trials on each test.
Reliability typically varies from a low of .94 to a high of .99.
coefficients are computed for all tests to determine their
interrelationships or lack thereof.
Multiple or logistical regression analysis is used to derive equations
to predict the
performance of individuals on the
work sample test who have only taken the JSES.
Validity is assessed
by statistical analysis as to how well each regression equation is
predictive of work
sample performance. A perfectly predictive equation would have an R2
1.0 and an R2 of 0.0 would
indicate that the equation had no ability to predict at all.
Setting cut-off scores
is a particularly complex area of test construction. MED-TOX utilizes
of evidence to arrive a cutoff level that is consistent with business
necessity. The cut-off scores permit the
selection of qualified workers, are based on the results of the task
analysis, and on the performance of
currently employed workers and their judgements as to what constitutes
acceptable performance. As each
test validation situation is unique, no perfect formula can be offered
in advance here.
validation work has been completed, there is no need to repeat the
validation process for
individual school districts that wish to start a new testing program.
Work by the North Bay Schools
Insurance Group, the San Mateo Unified School District, the Hemet
Unified School District, the Sacramento Schools Insurance Authority,
Contra Costa County Schools
Insurance Group has resulted in a transportable test that should be
equally useful for any school
district. To date, more than 86,000 school district job applicants have
been tested using the Jackson Strength
Evaluation System. Nearly every month a new district or employee group
brought into the testing program.
School districts use
different methods of implementation. In Sonoma, school districts use
medical providers to administer the tests. In Contra Costa and
Sacramento counties, tests are administered
by the insurance JPA. In Sacramento, the Schools Insurance Authority
has three large testing rooms that are
testing more than 100 job applicants a week for school districts in
Sacramento and El Dorado County.
Strength testing job
applicants is the single most cost effective intervention an employer
can make to reduce
workers' compensation and other injury-related costs. The relationship
between musculoskeletal injuries and
lack of strength has been repeatedly demonstrated (Chaffin, 1991).
Stronger and fit workers are more
productive and sustain far fewer back injuries than weak and unfit
Strength tests permit
the selection of individuals most likely to be
able to perform the tasks without undue
risk of injury to themselves and to screen-out persons who do not
possess sufficient physical ability to
adequately perform the job.
For further information, contact MED-TOX.
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