The need for physical
testing for workers in manual materials handling jobs has been
by risk managers, personnel specialists, physiologists, occupational
and ergonomists increasingly over the past few years. Each of these
have independently come to recognize the benefits to both the
being tested and the organizations themselves. Risk managers have an
in job safety and reducing workers' compensation costs. Personnel
seek to hire the most qualified individual available, reduce
and sick leave, and yet comply with state and federal EEO mandates.
and physicians seek to reduce unnecessary injuries and find ways to
predict in advance those most likely to become injured. Ergonomists
to study individual jobs and find ways through either job redesign or
selection systems that can better match the worker to the work.
Cognizant of these
issues, MED-TOX Health Services has developed an approach to assist
in the validation of physical ability tests for new hires. Since
injuries account for a large number of all work-related back injuries,
it makes sense to reduce the potential for overexertion. Hiring workers
with the adequate strength to perform the job is one way of reducing
injuries. A valid strength test, therefore, can reduce injuries in jobs
for which high levels of strength are required. The MED-TOX approach
- Provide employers
with a valid and legally defensible job analysis of the critical and
frequently performed, and physically demanding tasks associated with
- Provide employers
with a physical ability test that is job-related, valid, and reliable
can confidently be used in the selection of individuals for physically
The MED-TOX approach
is chosen on the basis of safety, reliability, and validity.
and reliability is discussed below. Ability tests are safer than work
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
applicant does not have the necessary strength to lift the weight he
become injured during the test. Using an ability test allows the
to determine if the applicant can only lift 20 lbs or 200 lbs. in a
efficient and standardized manner.
The MED-TOX approach
presented here is a criterion-related validation methodology. The
is designed to ensure that the ability test (selection device) is
demonstrated to be related to the job. The empirical linkage between a
given job and a given test is not insignificant. Often testing
or otherwise) is based on "face validity." Face validity is not
recognized by the courts and has been described by experts as a claim
in the absence of meaningful data.
ability tests can be subjected to a high standard of legal and
review, empirical evidence is usually necessary to show
A high standard of evidence is also necessary since all tests of
show adverse impact against females. Since a showing of adverse impact
requires the employer demonstrate job-relatedness, documentation
such a relationship becomes crucial.
Once and employer's
job has been selected for study, it is necessary to conduct structured
group interviews with workers from that job. The job analysis inquiry
directed at collecting tasks which require static strength. Static
involves the continuous exertion of maximum muscle force for a brief
time. Tasks that involve the lifting, pulling, pushing, or carrying of
objects and materials require static strength.
group interview, workers and the MED-TOX representative go to
storerooms, and other work areas to directly examine tools, equipment
materials that had been described by workers during the meeting. An
scale and/or a force gauge is used to directly weigh as many of the
objects as possible. If additional materials or tools are found that
also lifted, these objects are weighed, the weights recorded, and the
tasks added to the task listing. Multiple job analysis meetings may be
necessary if there are several different geographical locations or
differences facilities or number of employees in each location. Once
meetings have been conducted, a task inventory is produced. A task
is a listing of all the task collected. Task inventories are generally
subject to several review phases prior to worker surveys.
In order to measure
a job, one needs a measuring tool. Rating scales are the most useful
tools 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,
at a minimum it is important to illicit from workers:
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- Whether or not the task is
- How far the object is carried;
- How often the task is performed;
- How important the task is to the
- Whether persons who efficiently
perform the task are more capable than workers
who have a difficult time performing the task.
A random sample of
workers completes the task inventory. The responses are entered into
a statistical software program for data analysis. The first step in
data analysis is the computation of the percentage of workers that
individual task. Tasks performed by less than 50% of the workers are
eliminated from further consideration. Means are next computed for each
(How Far, Frequency, Importance and Proficiency). Next, a criticality
index is calculated. This index is the product of the mean Importance
the mean Frequency rating. This product is then multiplied by the
percentage of workers who indicate they performed the task and divided
by 100. Thus,
greater weight is given to tasks performed by all workers and less
weight is assigned to tasks performed by fewer workers. Tasks performed
workers are more likely to be critical and essential core job tasks
than those performed by only some workers. Tasks with high criticality
are identified as essential job functions.
which static strength tasks are critical for the job, it is next
to determine which tasks are suitable for utilization as work samples.
Ideally, the tasks selected should be among the most demanding tasks
are expected to perform. Additionally, other criteria should be
- Safety to
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
be those which can be completed in a reasonable amount of time.
scoring and clarity of results. Tasks selected should be amiable to
an unambiguous scoring or rating system. There should be no
as to what constituted various levels of performance. Subjective
on "style of lifting" or "ease of lifting" are less
suitable when objective measures are possible.
and low cost of equipment. The materials necessary for task
should be readily available and inexpensive.
The tasks selected should be as simple as possible from both the point
of view of instruction to incumbents and administration of the work
The tasks selected should be commonly performed by as many workers as
that meet the criteria can be categorized in a variety of ways. For
all tasks involving the use of a wheelbarrow might form a group or task
category. Alternatively, all tasks that involve work at particular work
site, or all tasks performed while unloading a box car or repairing
equipment could form other groups. The nature of the job and tasks
typically lend themselves to the selection of appropriate task
Task categories are important because they help the analyst organize
work and ensure that a variety of lifting tasks can be used to
work samples. An example of a category might be:
Gallon Container (Paint, Joint Compound, Floor Sealer) Tasks
- Lift/carry a five gallon can of
floor sealer (approx. weight 46.3 lbs.).
- Carry a five gallon bucket of
(approx. weight 55.4 lbs.).
- Lift/handle a five gallon bucket
joint compound (approx. weight 51 lbs.).
- Lift a five gallon bucket of paint
into the back of a vehicle (approx. weight 55.4 lbs.).
- Lift a five gallon bucket of paint
up onto a stack of other five gallon paint buckets (approx.
weight 55.4 lbs.).
Work samples may then be developed
from these categories of common critical tasks. For example,
a work sample constructed from these tasks might be constructed as:
Approach a row of
four five-gallon buckets of material. Stack three of the buckets on
top of one of the buckets of paint. Take the top bucket of paint off
stack and carry it to the truck bed. Set it down and release grip.
paint can and return to the stack of three. Place the can beside the
and replace the two remaining cans on the ground in a row, as they were
Static Strength Tests
MED-TOX has used
the Jackson Strength Evaluation System (JSES) in several projects and
found it to be a valid and reliable predictor of the ability of
to perform lifting, push, pulling, and carrying task.
The JSES was
by Dr. Andrew S. Jackson of the University of Houston. It features an
load cell to ensure accurate and reproducible readings of isometric
Large readouts allow determination of both peak and average strength in
pounds. The system includes the control and load cell, a hand
fixture for the measurement of grip strength, and a heavy duty lifting
platform, bar and chain. The manufacturer reports that the JSES is
used to measure static strength using the National Institute of
Safety and Health (NIOSH) protocol.
The JSES has three
qualities that make it ideal for employment testing. It has been shown
to be safe, reliable (r = .90), and practical. Results should be
obtainable within 15 minutes. The JSES is widely recognized as a
and valid indicator of the amount of static strength possessed by
At the present time many industrial medical clinics and employers are
the JSES. The test is relatively inexpensive (it can be obtained for
than $4,500), it is practical, safe and portable. Normative data for
the JSES can be viewed by clicking
In 1995, the EEOC
issued guidelines which attempted to clarify the difference between a
test and a physical ability test. According to the EEOC a medical test
was more likely to measure an individual's "physiological response"
to performing a task whereas a physical ability test measured task
directly. MED-TOX questioned the EEOC as to whether the JSES would be
a medical or physical test since it measured an individual's strength
physiologic response) and was not a direct measure of a particular task
but could predict performance on a variety of lifting tasks. In a
7, 1995 letter to MED-TOX, the EEOC stated:
The answer to your
inquiry concerning the Jackson Strength Evaluation System (JSES)
on the context in which this test is given. For example, if the JSES is
used simply to determine whether a person is capable of lifting a
pound box and carrying it twenty feet, the test would not be considered
"medical" and could be administered pre-offer. In this context,
it would not be dispositive that the test is used or interpreted by a
professional. Similarly, the score one achieves on the test -- provided
the only thing being measured is the amount of weight the person can
-- does not render the test a medical one even though, as you put it,
is being measured. As the Enforcement Guidance illustrates at pages 14
and 15, an assessment of whether a person can lift a fifty pound box is
a physical ability test as distinguished from a medical exam. If you
to measure the person's heart rate after the act of lifting, you would
then be engaging in a medical examination. While the distinction may
subtle, it is legally significant and constitutes the difference
what can and cannot be done under the ADA before a conditional offer of
employment [EEOC, personnel communication to MED-TOX, December 7, 1995].
In other words,
the EEOC would permit the use of the JSES (in the pre-employment
to the extent that test performance was related to the ability of an
to perform a specific task or group of tasks. In order to establish a
between the JSES and work performance, it is necessary to conduct field
testing with workers (participants).
and Data Analysis
A stratified random
sample of experienced workers is typically chosen for testing. The
should consist of individuals from various ages, racial groups and both
genders. Of course, many organizations will not have a significant
of females for testing nor will they have individuals employed who
perform the job. Without representatives from these groups, it is more
difficult to set a defensible cut-off score. Therefore, we suggest that
administrative and clerical workers participate in field testing as
of a brief medical screening, informed consent, an explanation of the
and height and weight measurements. Next the participants are
the JSES. Participants exert a constant force for three seconds on the
four tests which used the lifting bar and for three seconds using the
dynamometer in accordance with the manufacturer's instructions.
connected to each load cell records the amount of force exerted in
of force. Peak and average force is recorded.
For the Grip
test, participants squeeze on the hand dynamometer first with the
dominant hand and then with the nondominant hand. For this test, peak
grip strength is recorded.
During the Arm Lift, participants
stand erect with palms up, their elbows at the side,
and forearms at a 90 degree angle to pull up on the lifting bar.
The Shoulder Lift
also requires the participants to stand erect but with their palms
down. The participants
then pull up on the bar as if lifting a jackhammer.
Pull requires the participants to sit on the ground with their legs
extended and their feet flush against the lifting platform which is
placed against a wall. Participants pull back with their arms and legs
The Leg Lift test
requires the participant to squat with the arms extended downward. The
lifting motion is entirely in the legs as they are straightened.
Three trials are
conducted for each participant on each of the five tests, with the
of the last two trials used as the score. Scores are recorded for each
are performed by the participants. The simulations consist of actual
samples of the job. Several events such as the Five Gallon Bucket Stack
described above will have been constructed. Participants are given
time to rest between events and to decline testing at any time. Two
use stop watches to record the time it takes for each participant to
each work sample. Times are averaged for both stop watches and recorded
as the score.
instructed not to run or to perform the work at an unnatural
Participants are asked to envision a day in which they had a lot of
tasks to perform. When one task was completed, other important tasks
to follow. Participants are instructed to work at what might be
a heavier than average pace, but not one that was unrealistic or
of the pace at which they might work on a busy day.
participants estimate their personal fitness level, the minimum level
performance that they would consider acceptable for each work sample,
realistic each work sample is, and additional questions that are
to assist in setting the cut-off score.
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
are computed for all tests to determine their interrelationships and
thereof. Multiple regression analysis is used to derive equations to
the performance of individuals on the work sample test who have only
by statistical analysis as to how well each regression equation is
of work sample performance. A perfectly predictive equation would have
an R-squared of 1.0 and a R-squared of 0.0 would indicate that the
had no ability to predict job performance at all.
scores is a particularly complex area of test construction. MED-TOX
multiple forms of evidence to arrive a cutoff level that is consistent
with business necessity. The cut-off scores permit the selection of
workers, are based on the results of the task analysis, and on the
of currently employed workers and their judgments as to what
acceptable performance. As each test validation situation is unique, no
perfect formula can be offered in advance here.
services in the criterion-related validation of physical ability tests.
The tests are based on a comprehensive job analysis and field testing
workers performing work samples and their scores on the JSES. The tests
will permit the inclusion of individuals most likely to be able to
the tasks without undue risk of injury to themselves and to screen-out
persons who do not possess sufficient physical ability to adequately