Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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RIGID ABDOMINAL PAD FOR LUMBAR/SACRAL SUPPORT
Background of the Invention
I. Field of the Invention
The present invention relates to a rigid
abdominal pad for a lumbar/sacral support to decrease
the risk of back or spinal injury arising from lifting
heavy objects, for example.
II. Description of the Prior Art
Musculoskeletal disorders are some of the
more common impairments in both male and female popu-
lations. Disorders of the back and spine make up the
largest fraction of the total category of musculo-
skeletal problems. These conditions also rank first
in cost outlays by industry. As a result, musculo-
skeletal disorders are among the most important
disease categories affecting both industrial economies
and various United States health reimbursement sys-
tems.
Indeed, low back pain is often believed to
be one of the most common causes of absence from work
in today's work force. It has also been estimated
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that about 20% of all occupational injuries in the
United States are back related and that about 70-80%
of the world's population will have suffered this type
of orthopedic problem sometime during their life.
Additional difficulties arise when the
related cost of back problems occur. Taking into
account the average hospital cost, salary compen-
sation, disability payments and replacement expenses,
the back ache poses itself as a destructive pathology
in the American workplace. It has been estimated that
such costs may be as high as $30 billion annually.
The etiology of back injuries are directly
related to muscular-skeletal disuse and misuse syn-
dromes, as well as the incidence of unpreventable
trauma. Chronic stress and strain demonstrated over a
period of years account for many degenerative related
back pathologies. The results of general muscular-
skeletal disuse and misuse manifest the eventual
disruption of the vertebral bodies resulting in
micro-fractures, herniation, and disk degeneration.
Certain of the risks of lower back pain
and/or injury may be minimized by selecting appro-
priate individuals to perform the task. It is also
desirable to provide education and training in the
proper methods of lifting. However, these approaches
are not widespread or properly followed in many
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instances and thus do not add much to the prevention
of industrial back injuries.
A more promising approach to reducing the
risk of lowèr back injuries has come from the recogni-
tion that the human trunk or torso functions similarly
to a resilient cylinder which can be made to stiffen
or relax. As the cylinder stiffens, the stress on any
given portion of the cylinder tends to spread out over
the whole of the cylinder thereby reducing the stress
at the given location. This situation similarly
occurs in the human body, whereby as the intra-
abdominal pressure (IAP) of the torso increases, the
load on the human trunk is transferred from the back
to the abdominal cavity. Specifically, (1) the spine
is essentially a segmented column supported by the
paraspinal musculature which attaches anteriorly to
both the thoracic and abdominal cavities; (2) actions
of the muscles through movement creates a rigid mass
with the capability of transferring forces from the
spine to the trunk; (3) contraction of the trunk
musculature creates a system of pressurized rigid
chambers in the thorax and abdominal cavities which
are filled with air and a semi-fluid mass, respective-
ly; and (4) IAP increases with the strain of muscle
contraction.
It has been known to artificially induce
some increase in IAP by compressing the abdomen with a
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belt or corset tightened about the waist. An example
is the well-known weight-lifters belt which is gener-
ally comprised of a leather strap with a widened
portion adapted to be situated over the wearer's back
and across the spine. Another device promoted widely
for industry is known as the CompVest back support
available from Comp Equipment Corporation, 1473 Energy
Park Drive, St. Paul, MN 55108. The CompVest device
is made of a light weight nylon mesh with anterior
velcro closures and has a front portion adapted to be
situated between the ribs and the pelvic bone and a
rear portion adapted to overlie the back and spine and
the upper buttocks.
With the conventional weight lifters belt or
the CompVest device, tightening of the device about
the waist has been suggested to increase IAP thus
shifting some of the load from the spine to the
abdominal cavity. However, even with the increase in
IAP induced by compressing the waist, the stresses
associated with lifting even normally encountered
loads is believed to require more support than is
provided by the belt or vest device. Specifically, it
is believed that the spine and the trunk musculature
must still bear an inordinate load thereby not suffi-
ciently reducing risk of lower back pain and/or injury
during normal lifting procedures. Similarly, the
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musculature is thus strained and may fatigue or become
injured.
Some belts or corsets have also been util-
ized to force proper posture for lifting. For exam-
ple, a conventional weight lifters belt does not
generally promote proper lifting posture. Welsh U.S.
Patent No. 4,543,370 proposes to modify such a belt by
equipping it with a wide front portion which contacts
or overlies the sternal half of the tenth rib and the
anterior portion of the iliac crest in the pelvis.
The wide front portion acts to restrict excessive
forward bending and thus promotes proper lifting
posture. While forcing the abdomen to remain substan-
tially straight, the approach suggested by Welsh to
accomplish this result is not believed to be desir-
able. Contact by the front of the belt with the bony
prominences about the abdomen is generally uncomfort-
able and may cause injury or lead users to stop
wearing the belt. Further, that contact may lead to
loss of consistent pressure distribution within the
abdominal cavity. Such contact also limits the extent
to which the front of the belt may be tightened
against the abdomen. Hence, to promote proper posture
as suggested in the Welsh patent may reduce the
benefit available with a conventional weight lifters
belt. For example, to obtain desired increases in IAP
may require that the musculature absorb even more of
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the load then may be required of conventional weight
lifters belts. Thus, in view of the state of the art,
there is definitely a present need for a device which
can increase intra-abdominal pressure and promote
proper posture while reducing risk of injury or
fatigue.
Summary of the Invention
We believe that greater intra-abdominal
pressure increases may be induced with less risk of
injury than provided by the above devices. We further
believe that proper lifting posture may be promoted
without the drawbacks encountered by contact with
abdominal bony prominences. In its broadest sense,
the present invention accomplishes these desirable
ends by the provision of an accessory for a conven-
tional weight lifters belt or the like by which to
provide a rigid bearing surface for a substantial
portion of the abdomen during lifting. Specifically,
we provide a rigid pad sized to fit between a person's
abdominal bony landmarks and having a generally flat
surface to mate with and overlie a substantial portion
of the abdomen such that the belt or similar structure
sandwiches the pad between the belt and the fleshy
portion of the abdomen. Preferably, the pad is
mounted to a conventional weight lifters belt.
In contrast to a weight lifter's belt and
the CompVest device, the pad of the present invention
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is inflexible and, thus, will not tend to warp or
twist or otherwise deform when the abdomen bears
against it during lifting. Hence, the rigid pad
provides for uniform compression over the abdomen when
the belt is tightened. Further, the pad provides a
stiff surface against which the abdomen bears during
lifting thereby urging the torso to maintain a gener-
ally linear orientation which cannot readily bend or
flex about the longitudinal axis of the rigid pad such
as is otherwise possible with a conventional weight
lifters belt for example. Thus, rather than rely upon
contraction of the trunk musculature to increase IAP
as the person attempts to lift a load, the abdomen may
bear firmly against the surface of the rigid pad to
increase IAP, thereby relieving the spine and muscula-
ture of part of the load. In particular, the pad of
the present invention is believed to provide a substi-
tute "wall" to induce an increase in IAP with less
musculature tension or effort in the torso than
previously required. The increased IAP with less
trunk musculature contraction is believed to advanta-
geously reduce stress or strain on the lumbar/sacral
area thereby reducing risk of lower back pain or
injury while also limiting the risk of fatigue or
injury to the musculature.
In a preferred embodiment, the pad provides
a substantially flat surface which extends over a
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ubstantial fleshy portion of the abdomen and between
the bony prominences about the abdomen such that as
the wearer of the pad bends to lift a load, the bony
prominences move into or toward the edge of the pad.
To avoid discomfort, the surface of the pad flares
away from the body at the edges or corners adjacent
the bony prominences. Thus, the surface of the pad
preferably extends over most of the abdomen between
the ribs and pubis with the angled corners extending
from the lateral edges of the pad so as to lie out-
wardly of and angled away from the abdominal bony
prominences. In this way, the abdomen may bear
against the pad without the pad also undesirably
contacting abdominal bony prominences. In a preferred
embodiment where the pad is rectangular in shape,
notches or gaps are cut into the pad between pairs of
the angled corners extending from the corners to
define strap slots along the sides of the pad through
which the strap of the belt may be snugly received to
thereby mount the pad to the belt.
Experimental studies with a rigid pad
according to the principles of the present invention
show it to be effective in enhancing force production
of the torso of the humans tested and, thus, suggests
that lower back pain and/or injury can be reduced to a
level and extent not previously thought possible or
achieved.
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These and other objects and advantages of
the invention shall be made apparent from the accompa-
nying drawings and the description thereof.
Brief Description of the Drawings
The accompanying drawings, which are incor-
porated in and constitute a part of this specifica-
tion, illustrate a preferred embodiment of the inven-
tion and, together with a general description of the
invention given above, and the detailed description of
a preferred embodiment given below, serve to explain
the principles of the present invention.
Fig. 1 is a perspective view from the front
of a preferred embodiment of an abdominal pad con-
structed in accordance with the principles of the
present invention;
Fig. 2 is a side elevational view of the
abdominal pad of Fig. 1;
Fig. 3 is a partially cutout, rear eleva-
tional view of the pad of Fig. l;
Fig. 4 is a perspective view of the abdomi-
nal pad of Fig. 1 in combination with a weight lifters
belt to provide a lumbar/sacral support in accordance
with the principles of the present invention;
Fig. 5 is a side view of the support of Fig.
4 properly secured about the waist of a human standing
erect;
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Fig. 6 is a front view of the support of
Fig. 4 properly secured about the waist of a human
standing erect; and
Fig. 7 is a view like Fig. 5 showing the
human abdomen bearing against the pad of Fig. 1 in
response to lifting stresses as contemplated by the
present invention.
Detailed Description of the Drawinqs
With reference to Figs. 1-3, there is shown
a rigid abdominal pad 10 constructed in accordance
with the principles of the present invention. Pad 10
includes a rigid plate 12 having an outer bearing
surface 14. Conforming to plate 12 upon bearing
surface 14 may be an outer cushion 16. Plate 12 may
be formed from a ~ inch thick stiff plastic such as
polypropylene. Cushion 16, which overlies bearing
surface 14 and conforms to the shape of plate 12,
provides a comfort surface for the user and may be
formed from a 3/16 inch thick slab of aliplast secured
to plate 12 such as by glue (not shown).
Bearing surface 14 is defined between longi-
tudinal superior or upper edge 18 and inferior or
lower edge 20 and lateral left and right edges 22, 24,
respectively. The dimension of pad 10 between those
edges is selected for proper anatomical fit and com-
fort against the human abdomen (see Figs. 5 and 6) so
as to overlie a substantial portion of the abdomen
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between the pubic symphysis and xiphoid or lowest part
of the ribs on the one hand and the iliac prominences
or crests on the other hand, i.e., between the bony
prominences about the abdomen. Between these bony
landmarks of the abdomen is an area of the abdomen
that does not closely overlie any bone structure.
This area is referred to herein as the fleshy portion
of the abdomen. Preferably pad 10 is sized to overlie
a substantial portion of this fleshy portion. The
following is a table of preferred dimensions, in
inches, of pad 10 for various size men and women
wherein vertical is between edges 18 and 20 and width
is between edges 22 and 24:
MEN
SMALLMEDIUM LARGE X-LARGE
Vertical 4 3/46 1/4 7 7 1/4
Width 5 6 1/2 7 1/4 7 3/8
WOMEN
SMALL MEDIUM LARGE X-LARGE
Vertical 4 1/2 6 6 1/2 6 3/4
Width 5 1/2 7 7 1/4 7 3/8
Thus, pad 10 generally is between four to seven inches
measured vertically and five to eight inches measured
horizontally.
To avoid impinging the bony prominences or
snagging any skin or fat about the abdomen while using
pad 10, pad 10 is provided with transition zones at
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the periphery thereof. These transition zones are
preferably accomplished by angling the upper and lower
corners 26, 28 of pad 10 away from bearing surface 14.
Due to the size of pad 10, corners 26, 28 would, if
planar to surface 14, undesirably impinge against
abdominal bony prominences during lifting. However,
corners 26, 28 are sufficiently angled so as to extend
over and away from such bony prominences so that as
the user bends, undesirable contact with bony promi-
nences 84 is avoided. In particular, superior corners
26 flare away from the subcostal angles of the human
ribs 94 so as not to impinge on the ribs during
lifting. Similarly, inferior corners 28 flare away
from the pubis to avoid impinging the pelvic 96 or hip
bones during lifting. Further, the entire inferior
edge 20 preferably flares away from surface 14 to
avoid impinging against the pelvis and, in particular,
the iliac prominences or crests during lifting. Upper
edge 18 may also have a slight flare to avoid imping-
ing against the upper abdomen during lifting.
In a preferred embodiment, C-shaped notches
32 are formed in pad 10 between each pair of corners
26, 28 to receive a strap portion of a belt as will be
discussed. C-shaped notches 32 are defined between
generally parallel, upper and lower edges 34 at
corners 26, 28 and perpendicular bight edges 36
therebetween. Bight edges 36 are preferably bevelled
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away from bearing surface 14 as at 38 to allow the
belt strap portion to better conform to pad 10.
Pad 10 is preferably mounted to a retaining
structure such as a conventional weight lifters belt
40 as shown in Fig. 4 to form a lumbar/sacral support
42. Belt 40 includes an elongated leather strap 44
having an enlarged or widened portion 46 centrally
located between outer ends 48, 50 of strap 44. To
mount one end 48 of strap 44 to pad 10, end 48 is
fitted into notches 32 on pad 10 such as by being
pressed into place therein between respective edges
34.
Although not necessary, belt 40 may be held
to pad 10 with a clip or other retaining structure
(not shown) secured to front wall or non-bearing
surface 60 of plate 12. As will be appreciated, such
retaining structure may take any one of a number of
forms such as a resilient clip, strap or loop and pile
velcro fastener, to name but a few.
To secure pad 10 against the abdomen, belt
40 may include any conventional means for fastening
one end 48 to the other end 50. In the illustrative
example, belt 40 is provided with a buckle 70 mounted
to strap end 48 by a leather keeper 72 and a plurality
of holes 74 formed in end 50 to receive teeth 76 of
buckle 70 to form a conventional belt fastener. As is
well understood, ends 48, 50 may alternatively be
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joined together by Velcro fasteners with loop and
keeper (not shown) or any other fastener which will
permit belt 40 to be securely fastened about the waist
as will now be described.
Pad 10 is positioned centrally over the
fleshy portion 80 of abdomen 82 and between abdominal
bony prominences 84 of a human subject 86 such that
bearing surface 14 of pad 10 faces the subject's
abdomen 82 and corners 26, 28 are adjacent bony
prominences 84. Belt 40 is placed about the human's
waist 90 such that widened portion 46 of belt 40
overlies lower spine portion 92 as seen in Fig. 5 and
strap ends 48, 50 overlie pad 10 to hold pad 10 over
fleshy portion 80 of abdomen 82 and between the
abdominal bony prominences 84 such as the xiphoid or
ribs 94 and pelvis 96 as seen in Fig. 6. Although
intimate contact between surface 14 and abdomen
portion 80 is acceptable, cushion 16 is provided
therebetween for comfort. Further, a shirt (not
shown), for example, could be worn between pad 10 and
abdomen 82 although cushion 16 is sufficient to
provide a comfortable surface against abdomen 82.
Once properly positioned, belt ends 48 and 50 are
brought together and tightened in conventional manner
such that abdomen portion 80 is compressed by pad 10
from its nominal outwardly-bowed orientation as shown
in phantom line in Fig. 5 to a substantially planar
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and vertical orientation as shown in solid line in
that view. Belt 40 is properly tightened when slight
bending of subject 86 causes abdomen portion 80 to
bear against pad 10 such that abdomen 82 is restrained
from bending or flexing about longitudinal axis 30 of
pad 10.
As subject 86 tries to bend at the waist as
shown in Fig. 7, abdomen portion 80 will bear against
surface 14 of pad 10. This bearing contact will tend
to prevent the abdomen from bending thus encouraging
proper lifting posture by urging trunk 98 into a
substantially linear orientation between the chest 100
and hips 102. And as the trunk 98 rotates between
positions shown in Figs. 5 and 7, the flaring of
corners 26, 28 prevent undesirable contact with bony
prominences and further avoids biting contact between
pad 10 and any flesh or fat about the abdomen.
Similarly, flaring of inferior edge 20 reduces blting
contact between pad 10 and the pubic area of the human
as might otherwise occur if edge 20 were not flared.
In use, as subject 86 bends over and tries
to lift a load (not shown), abdomen portion 80 will
bear against surface 14 of pad 10. Pad 10 is believed
to provide a wall which substitutes for trunk muscu-
lature contraction to thereby increase IAP without
undue musculature activity in the abdomen. The result
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is an increase in lifting capacity which is believed
to be attained with reduced risk of pain or injury to
the spine by better spreading stress from the spine to
the abdomen without injuring or fatigue of the muscu-
lature. That is, the present invention is believed to
result in elevating IAP without placing an undue load
or stress on the abdominal wall muscles. Thus,
instead of relying upon the musculature to contain and
compress the abdomen to transfer force from the spine,
the rigid pad 10 is provided for this purpose.
The particular shape of pad 10 is of further
advantage in providing a maximally stiff and large
plate 12 to compress as much of abdomen 82 as possible
while avoiding the discomfort, potential injury and
limitation which may result from contact with abdomi-
nal bony prominences.
Examples
Ten well-conditioned males between the ages
of 21 and 35 undergo isokinetic back testing under
three conditions. Each of the subjects is tested
without any support (control), with a CompVest device,
and with a support comprised of a rectangular rigid
pad held to the abdomen according to the principles of
the invention (experimental support).
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Reduction in trunk flexion forces is be-
lieved to be indicative of increased IAP. The iso-
kinetic back tests demonstrate trunk flexion forces at
various speeds of isokinetic resistance with the pad
as compared to the CompVest device and no device. The
results are statistically highly significant for the
various measures of average muscle torque, work and
power for trunk flexion at 30 per second as shown in
Table I:
TABLE I
Experimental
Measure CompVest Support Control
Torque/
Newton Meters213.43 200.95 222.92
Work/
Newton Meters262.38 246.24 272.42
Power/Watts 90.30 84.50 94.00
Measures at higher speeds of isokinetic resistance
(60/sec., 90/sec. and 120/sec.) are also found to
be statistically significant with the experimental
support. Trunk rotation of muscle torque is also
statistically significant. Also, grand means for peak
lifting force (Table II) and lifting power (Table III)
are found to be higher when subjects perform the
lifting task with the pad than without. The increase
in these measures are consistent with increased trunk
forces obtained during trunk extension trials when
subjects wear the pad as compared to the control:
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TABLE II
GRAND MEANS AND STANDARD DEVIATIONS-FOR
PEAK LIFTING FORCES (Values Expressed in Newtons)
Mean/SD
Speed of Mean/SD Experimental Mean/SD
Resistance CompVest Support Control
30 inches/sec 1373.71 1420.44 1325.21
(318.70) (290.71) (322.35)
TABLE III
GRAND MEANS AND STANDARD DEVIATIONS FOR
LIFTING POWER (Values Expressed in Watts)
Mean/SD
Speed of Mean/SD Experimental Mean/SD
Resistance CompVest Support Control
30 inches/sec 732.60 766.60 712.20
(211.32) (177.16) (171.01)
The results suggest that the capacity to
increase lifting forces are enhanced with the present
invention. The results also suggest that the present
invention provides increases in IAP with less stress
on the musculature than provided by the prior art.
The results further suggest that less musculature
activity is required to lift the same load with a pad
according to the invention than with the CompVest
device of the prior art or with no support. This is
believed to reduce stress on the back or spine and,
thus, reduce risk of injury thereto. It is also
believed that if the musculature were to become more
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involved, the present invention would result in an even
greater IAP than possible with prior art devices, thereby
further reducing stress on the back.
Further analysis and detail of such studies may be
found in the thesis prepared by Michael L. Woodhouse, one of
the inventors herein, entitled "The Effects of Various
Lumbar/Sacral Back Support Systems Upon Human Peak Muscular
Force, Total Work, and Average Power" submitted to the
faculty of Old Dominion University. A copy of the thesis is
submitted with this application for patent.
Additional advantages and modifications will
readily appear to those skilled in the art. The present
invention in its broader aspects is therefore not limited to
the preferred embodiment and illustrated examples shown and
described. Accordingly, departures may be made from such
details and/or departing from the spirit or scope of the
present invention.
sg/lcd
