For Certified Professional Ergonomists, CPE’S
Causal Factors in the Performance of Anti-fatigue Matting.
Paper’s Summary:
First Supposition: In general and within extent, the higher the degree of polarity within an
ergonomic mechanism the more effective that mechanism may be.
Second Supposition: Effective ergonomic mechanisms depend largely on the symmetry between
their reciprocal factors. Beyond the Point of Symmetry, the factor in excess is largely ineffective.
Third Supposition: High degrees of both cushion and support are determinative factors in the
performance of certain ergonomic mechanisms that include anti-fatigue matting. The effectiveness
of the mechanism is limited by the lesser factor. Imbalance between the factors may range from
ineffective to detrimental.
Part I. The Beginning.
1. Empirical Knowledge.
How many auditoriums, meeting rooms, theaters, buses, trains, or even restaurants have
signs at the door that say, “Everyone Shall Sit?” None. The signs are not necessary.
People naturally sit. Standing for long periods of time - more than about ten minutes induces a desire for seating.
It’s also true that people who work would rather sit than stand. Consider that even large
strong professional football players can be seen sitting-down when there is no action.
It doesn’t take a scientific paper. Empirical knowledge is enough to conclude that people
who have been standing for a long period of time become quite conscious that they have
been standing for a long period of time. In other words, there is a certain degree of
discomfort associated with prolonged standing.
2. Comparing Apples.
The time spent being conscious of the discomfort from standing is time lost from fully
concentrating on other matters. Imagine two equal groups of people. Each group watches
the same two-hour documentary. One group stands for two hours. The other group sits.
At the end of the film, each person is tested on content. Overall, the group that sat scored
higher than the group that stood. Surprised?
The next day the same two groups sit and listen to an eight-hour lecture filled with little-known
historical facts. The higher-scoring group is required to sit on hard concrete benches for eight
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hours. The lower-scoring group is given comfortable chairs. In the end, the group sitting on
comfortable chairs scored higher than the group sitting on concrete benches. Surprised again?
The fact is: there are a great number of factors involved when comparing apples, seating and antifatigue matting.
3. Subjective Truth.
It’s noted that ergonomics has a subjective element to it. When a person says, “I’m feeling better,”
we would say, “Great!” We would accept the statement as true that the person is feeling better.
We would not ask him or her to prove it with scientific data. In other words, when it comes to
ergonomics, the bottom line is how the individual feels during work, at the end of the day and over
time.
4. Understanding Causation.
Imagine the Boeing Company making aircraft without understanding the cause of lift. It
sounds preposterous. But a literature search reveals that mat manufacturers have written little- even
speculatively- on the issues of causation with respect to effective anti-fatigue matting.
Even the academic literature falls short, making only vague references to “material,” “thickness”
and “firmness.” (1)
Understanding causation is essential in the design for the anticipated performance of any product.
This paper will discuss the probable causes of performance in anti-fatigue matting.
Part II. The Major Factors.
1. The Mechanics of Anti-fatigue Mats.
Stepping on a mat produces a reaction or response within the mat. Identifying the reaction is
important because within that reaction are the causal elements of its performance. The reaction can
be identified by eliminating what it is not. The reaction is not thermal. Nor is the reaction
chemical, visual or radioactive.
Clearly, the best description of the reaction within a mat is “mechanical.” In other words, the mat
physically does something as a result of forces placed upon it. All mechanical functions are
measurable and good to be measured for reference in the future.
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2. Cushion and Firmness.
What happens when force is placed upon the mat?
The mat first compresses. Cushion, or compressibility, is an important mechanical factor in antifatigue matting. It provides the “give”- like stepping on soft earth- to an otherwise hard and
unforgiving floor surface.
“Cushion” may have complicated definitions such as,
“the compliance of the mat measured as the ratio
of its displacement to load at the peak load.” (2)
But for most of us, cushion is simply how much the mat “gives” (under a controlled force).
Firmness is the other side of the mechanical coin. Without resistance to compliance, a mat would
simply bottom-out under the same force that facilitated its compliance.
The method of testing for firmness must parallel the method of testing Cushion. Again, there are
specific definitions such as,
“Creep relaxation… a parameter reflecting the relaxation of a mat
as expressed as a percentage to maintain the constant force.” (3)
But most of us know “firmness” as an increase in resistance against mounting compression,
i.e. “support” or not “bottoming-out.”
The combination of Cushion and Firmness are the two basic responses of a mat that is suppose to
have anti-fatigue qualities. The two qualities are indeed mechanical.
3. The Mechanical Cycle of the Mat.
Everything mechanical has a cycle. The cycle might be up-and-down, in-and-out, left-and-right or
even circular. Every mechanical cycle has two reciprocal ends, e.g. farthest in/furthest out.
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Cushion and Firmness are mechanically reciprocal, opposite to each other in function, and each
with a separate and final peak of measure.
Certain qualities of a mat can be predicted by the measure of its reciprocal factors, cushion and
support. The length of a cycle is the combined measure of the reciprocal factors, each measured
from the center. The opposite ends of a cycle measured together are its polarity. Polarity is
important because it represents the high measure of the combined factors.
Consider the two drawings below. They represent two models for mat products with different
degrees of cushion and support.
One model has greater degrees of cushion and firmness than the other model. That same model has
a higher degree of polarity within it. Model 2 is, of course, the preferred because it has more of
what is wanted.
First Supposition: In general and within extent, the higher the degree of polarity within an
ergonomic mechanism the more effective that mechanism may be.
4. The Very Important Requirement of Symmetry.
Well-working mechanical functions necessarily require symmetry within the cycle. Consider that
the distance a rod goes up must equal the distance the rod goes does down. The length of an
extended arm must equal the distance of its retreat. The point on a wheel must come back to the
point of its beginning. Any mechanical model without symmetry will fall between being inefficient
to failing.
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Let’s say we’re in the market for a manual water pump based on specifications. We are told to
consider a pump that can take-in and hold 10 gallons. But we discover that the same pump is
capable of releasing only ONE gallon at a time. The net result is that nine of the ten gallons is
rendered useless because of the limits of one factor.
Similarly, consider a steering wheel capable to turning ninety degrees to the left, but only ten
degrees to the right. That mechanism would be not only inefficient, but dangerous.
Now consider an anti-fatigue mat that scored a “20” for compressibility and a “90” in its firmness.
What would one conclude in that mat’s predictive performance?
Look at the three models below, understanding that “A” and “B” are factors that are meant to be
reciprocal. Which model would work best? Would you change your mind if some salesman told
you that the third model had the greatest degree of any single one factor? No. Of course not- it’s a
bad water pump.
5. The Point Symmetry.
The definition of “reciprocal” is important and relevant. A reciprocal is the “multiplicative inverse
of another number, function or factor.” By definition, if one factor goes up by “X” the other
reciprocal factor must inversely go up by “X”.
The real world of matting is not perfect. High degrees of cushion and support are major factors in
the performance of matting, but the degrees of each may not be reciprocal. Therefore, the
effectiveness of the mechanism is limited by the lesser factor. In other words, the lowest-commondenominator between the factors is its effective level of performance. If for example, Cushion is
measured at 40%, then the effective measure of Support stops at 40%, even if the actual measure of
support is higher. If cushion measures at 73%, then the optimum measure of support is 73%.
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The Point of Symmetry is the cut-off point for the factor in excess. Beyond the point of symmetry,
the excess in the second factor is largely ineffective.
Second Supposition: Effective ergonomic mechanisms depend largely on the symmetry between
their reciprocal factors. Beyond the Point of Symmetry, the factor in excess is largely ineffective.
5. The Detrimental Imbalance of Excess.
Some ergonomic products work better than others. Consider an extreme example of a waterbed to
illustrate poor ergonomics in flooring. At ten inches high, the waterbed would have a great deal of
cushion, about 90%. But without certain density and other physical properties, its support would
measure maybe only 20%. A person standing on the waterbed would sink inches with every step.
The process of movement would become exhausting. The excess cushion would be not only
ineffective, but actually detrimental. See the graph below:
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Concluding Supposition: High degrees of cushion and support are determinative factors in the
performance of certain ergonomic mechanisms that include anti-fatigue matting. The effectiveness
of the mechanism is limited by the lesser factor. Imbalance between the factors may range from
ineffective to detrimental.
Part III. The Importance of Timing.
1. Resilience.
Alone, high measures of cushion and firmness in a mat are inadequate if the mechanism itself fails
to respond in a timely manner consistent with the mass and movement of the body. In other words,
there are big and little people who move at fast and slow speeds. An effective ergonomic mat must
complete its cycle return to a neutral/ready state within a necessary time.
Mechanical timing in a mat is called resilience. The measure of resilience is especially important
when the ergonomic mat contains high degrees of cushion and support. A greater length of its halfcycle (cushion) necessarily reflects a greater length of the other half-cycle (firmness), making
important its cycle time.
Inversely, limited mechanisms will demonstrate a disproportionately high amount of resilience
because of their shorter cycles and required time for completion.
Part IV. The Final Considerations.
1. How Much Cushion and Firmness is Enough?
What is optimum compressibility of a mat? What is optimum firmness?
Consider this claim, “we have the optimum compressibility of any mat, between .6 and .9 megaPascal’s,” says a company. Sounds good, but the calculation turns out to be 87-130 pounds per
square inch. Surely, this statement is wrong because no one can exert that much force. The claim
is made without competence or truth.
The point is, if you’re sitting and making decisions about those who stand, be skeptical of claims
from companies- and certainly ask questions outside the claimer’s script. If you make decisions on
the floor, in practice, you can assume that you “got it” when your co-workers, from both sides of the
weight spectrum, say it’s good for them- empirically tried, empirically known.
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In general, light persons enjoy a lot of cushion; heavier persons require a lot of support. And
because that one mat must work of both, that mat should contain high degrees of both properties.
2. Is it only About the Material, or is it also About Design?
The issue of design in anti-fatigue mats is rarely examined. The lack of attention to design seems to
be because most anti-fatigue mats are made of solid foam.
Some have said that it is all about the material.
But first consider the achievement of the Golden Gate Bridge. The bridge employs a measure of
“compliance.” It bends downward under the weight of cars and trucks upon its surface. On the 50th
Anniversary the bridge was closed to traffic. On that day over a 100,000 people descended upon
the bridge in celebration. The bridge sagged more than ever in its history. Officials were worried
that the bridge would collapse. But the bridge, like a big spring, resisted the compression as the
compression increased. In other words, the reciprocal factor to compression, support, was fully
employed and in good balance.
Without design, the simple mass of steel and concrete would have had no function. If a design is
incorporated with the material it is because that material can be formed into a design, and the design
itself can further the materials’ efficacy beyond their raw form.
3. What Materials are Suited for Anti-fatigue Matting?
The material in an anti-fatigue mat should be alive. The material should be able to stretch, push,
bend and twist. Equally important the material must have excellent memory, the ability to return to
its original form.
Consider the choices of material: wood, steel, rock, cloth, rubber and plastic. What material is most
alive?
It may be well to consider the material used in the soles of athletic shoes since athletic shoes are
about as close as it gets to the function of anti-fatigue mats. Ergonomic mats simply augment the
function of good soles by way of greater capacity in volume and design.
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4. The Quality of that Material.
A class of material, whether concrete or rubber, is a general classification. The quality of the
material within a class may vary substantially.
For example, rubber can be easily diluted with inexpensive fillers, such as clay and sand. A visual
inspection of the product will not reveal its content. Therefore, it is important to know the quality
of the material. The quality of any material can be inferred by knowing its physical properties.
One would want to know its hardness, relative heaviness, its strength at stretch, how much it can
stretch, when it will tear, its resistance to abrasion and its long-term memory, among others. These
questions can be answered under Hardness, Specific gravity, Tensile strength, Elongation at break,
Tear resistance, Abrasion resistance, Compression set, etc.
A clean-room certification is a good indication that the material is “clean” and “strong,” without
filler.
5. Profile or thickness.
Thickness is a static measure. It is not a measure of performance. Resilience is a measure of
performance. Tear resistance is a measure of performance. To infer that the thickness of a mat is
an indication of a mat’s performance may have at most some marginal truth, but generally is
erroneous.
The more efficient the mechanics within a mat, the lower its profile may be. Mats with higher
profiles are generally less efficient. Higher mats also create a greater risk for tripping. Higher
mats may also create instability because of excessive unwanted lateral movement.
6. Slip resistance.
The subject of slip resistance in matting has been the subject of many articles, and is addressed only
briefly here.
With respect in matting, in excessively wet and oily environments, the major issue is preventing
slips. Slip resistance is best achieved by using a firm material that has a high coefficient of friction,
such as PVC tiles impregnated with Aluminum Oxide.
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7. Impact Absorption.
The issue of impact absorption is important in running shoes. But since workers do not run within
the facilities, this issue is nominally mentioned here. In general, anti-fatigue mats should be able to
absorb enough of the kinetic energy from a “direct strike” so that the impact of the strike goes
unnoticed, or is only mildly felt.
8. Handling Considerations and the Effects of Moisture.
Mats of supple material tend to be easy to handle during maintenance. Ease of handling is an
ergonomic issue.
Moisture underneath the mat will degrade foam backings, diminishing the mat’s performance.
Areas with surface moisture would do better with material that is non-porous, preserving the life of
the mat and its original performance.
End.
(1)
Redfern MS and Chaffin DB: The influence of flooring on standing fatigue. Human Factors.
37(3):570-81, 1995.
Redfern MS, Cham R: The influence of flooring on standing comfort and fatigue,” American
Industrial Hygiene Association Journal 61(5):700-708, 2000.
Cham R, Redfern MS: “Effect of flooring on standing comfort and fatigue,” Human Factors
43(3): 381-391, 2001.
(2)
The Role of Mechanical Properties in the Ergonomic Performance of Commercial Mats.
David Owens, Ph.D., Pasadena, CA April 1997
Written by
John Austin, J.D.
1/9/09
PO Box 861222
Los Angeles, CA 90086-1222
213-229-0830
John@Barefoot-Flooring.com
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Author’s Note.
This paper was written for several reasons. First I could find very little information on the subject
from the universities. Secondly, I found that the certain claims by manufacturers were baselesssimply marketing exploits made without foundation, standards or objectivity. Finally, there can be
no grade for quality if there is no standard for grade. There are no standards in this industry.
There are no guidelines. How can this be possible?