Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND¨FIELD OF INVENTION
This invention relates to the shape of the heel of footwear, specifically the
shape and proportions of
the elements of the heel of the footwear in the sagittal plane in relation to
the rest of the article of
footwear and the heel of the wearer. Said structure being that which does not
interfere with (allows)
the natural strike point of the heel in walking/running and allows the natural
controlled fall (roll,
declination...) of the front of foot. Said structure does not contribute to
shin splints or plantar
fasciitis by adding to the natural forces exerted upon the foot and appending
structures by increasing
the lever arm of the wearer's heel.
BACKGROUND OF THE INVENTION¨PRIOR ART
Previously the design of the heel of has generally been done with attention to
style, cushioning, and
some specialties such as the heel of a riding boot. Two medical problems have
arisen. The first is
known as Medial Tibial Stress Syndrome (MTSS), commonly called shin splints.
The below quote
by the Mayo Clinic staff says:
Shin splints are caused by excessive force (overload) on the shinbone and the
connective tissues
that attach your muscles to the bone. The overload is often caused by specific
athletic activities,
such as:
Running downhill
Running on a slanted or tilted surface
Running in worn-out footwear
Engaging in sports with frequent starts and stops, such as basketball and
tennis
Shin splints can also be caused by training errors, such as engaging in a
running program with the
"terrible toos" ¨ running too hard, too fast or for too long.
This is the generally accepted reasoning for the condition.
It is a fact that "Shin splints are caused by excessive force (overload) on
the shinbone and the
connective tissues that attach your muscles to the bone."
The reasons above following this statement could be contributors to the
problem.
There is a more basic and more important element.
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Shin splints refers to the condition of painful shins during and/or after
running or extended walking.
The cause of this pain is damage to the muscles and attachments of the
anterior lower leg or shins as
they are commonly called. This is medically documented and will usually heal
if running is ceased.
Why does this happen? It would seem running is a natural thing to do for
survival at least if not for
pleasure. The foot is a highly functional, evolved, biomechanical device. It
is well documented
that persons living in areas of the world where they largely go barefoot there
is little incidence of
shin splints, plantar fasciitis or other gait related pathologies or symptoms.
First to explain the functioning of a foot in the gait cycle in normal action
which would be bare foot.
At the beginning of the heel-toe type gait cycle one lands on the ball of the
heel Fig 2, and the foot
rolls forward over the round portion of the heel which is delineated by the
radius of the calcaneus
Fig 1 point (7). This rolling motion disperses or spreads out some of the
impact of the initial strike.
It also allows a gradual loading from the first touch to full loading of body
weight plus inertial
forces. In this motion the anterior muscles of the shin control the attitude
of the foot¨they hold the
front of the foot up through their attachments to the upper anterior foot
bones (22) against the
weight acting on the heel through the fulcrum of the calcaneus (2)-talus (4)
structure pivoting on the
talus (4)-tibia (6) joint. Point (12) is the approximate center of rotation of
the foot around the tibia
joint. The front of the foot would drop with a shocking splat on impact if not
suspended by the shin
muscles. This rolling action across the heel distributes the downward force of
the body's weight
while giving traction to the force generated by the leg muscles to contribute
to forward motion. The
shin muscles also act to absorb the shock of impact as they stretch with the
force of impact. In
actual heel strike walking or running there is not a great deal of movement of
the foot in relation to
the leg in the landing portion of the stride cycle. Under natural conditions
the shin muscles hold the
foot in place pulled up and under tension as the heel accepts the body weight
being transferred from
the opposite foot. This tension relaxes as the ball of the foot reaches the
horizontal plane, and the
foot takes on full body weight and then prepares for the push off portion of
the stride cycle.
Another important point in the cycle is that as the forefoot is closing with
the horizontal surface, the
toes are drawn up as the forefoot lowers in what is known as the Windlass
mechanism. This is
accomplished by muscles in the shin area as well. This pulling up of the toes
tightens the plantar
fascia (25) by pulling those tendinous tissues around the head of the
metatarsals (26) in a manner
somewhat like an old fashioned windlass. This pulls directly at the fascia
anchor point (24) on the
medial process of the tuberosity or posterior portion of the calcaneus just in
front of the weight
bearing ball shape. The tightening of the fascia draws up and tightens the
arch of the foot in
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preparation to accept full body weight. This happens as the knee moves over
the foot and full body
weight is applied. The foot takes the weight, the shin muscles relax and the
foot flattens and begins
to transfer to the push off position. The plantar connection with the forefoot
is a major stabilizer of
the calcaneus bone, which is bearing the weight of the body plus inertial
forces.
It can be seen that in the landing portion of the stride cycle the muscles of
the anterior portion of the
lower leg do a dual function of suspending the forefoot under load and
providing the tension to
stabilize the arch of the foot and the calcaneus through the plantar fasciae.
With each step the
anterior or shin muscles are heavily loaded.
As can be seen in Fig. 2 when the foot first contacts at point (16) there is a
given ratio of
leverage between the attachment area of the shin muscles (11) and the area of
the calcaneus that the
contact forces act on, (7). (Point 8 is a radius delineated by the calcaneus
and about half the
distance between the calcaneus and the outer non-weight-bearing heel. It
represents the moving
point of contact of the outer heel, which is compressed by body weight in
landing. 50% is an
estimated average of heel pad compression under weight.) As the foot rolls
forward on the round
portion of the heel (barefoot) the leverage against the shin muscles
decreases. The contact point
moves forward to point 14 where the curve of the heel meets the horizontal and
the foot is ready to
accept full body weight. This means that as the body weight borne by the
leading foot increases
(the weight of the body is transferred to the front foot as it moves forward
over the foot) the
leverage against the shin muscles decreases. Another way in which the leverage
is decreased in
heel strike running/walking is that in taking a stride the forefoot is
naturally lifted, to prepare for
contact, pivoting the front of the foot upward in relation to the leg which in
turn moves the heel
downward and forward. This forward movement of the ankle shortens the lever
arm lines (12-16,
17) at the time the foot first contacts giving a greater lever advantage to
the shin muscles. Fig. 2,
point (17) shows the lever extension of a bare foot contacting at a 45 'angle.
This is near the
maximum inclination and at this inclination the foot would not be supporting
much of the body
weight, as it would be too far out in front. These are significant changes in
lever advantage and are
very important as the heel can be subject to forces of 3-4 times body weight
on contact. The action
of running and walking at length is a highly repetitive action. Any imbalance
in forces acting on the
foot is repeated possibly thousands of times in a given period of activity.
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The aforesaid illustrates a workable system any footwear device should
endeavor to complement.
This means the optimum design for a shoe heel would be a shape closely
duplicating the contact
area of a barefoot with its point of contact corresponding to that of the bare
foot of the wearer. The
rounded heel takes advantage of the lessening lever arm. However any placement
of the contact
point near optimum will result in much less strain on the shin muscles.
So why does a natural motion like running or extended walking for some result
in damage
and pain in the shin muscles, connective tissue and bone? One of the only
workable but not
necessarily practical handlings, in running, for shin splints is to run
barefoot. Another is to increase
the strength of the shin muscles, another to learn to run landing only on the
forefoot. Shoes have
been designed to ensure landing only on the forefoot. Barefoot style shoes
that fit closely to the
foot have been found to help. These solutions work for some but the general
populace wants to be
able to walk or run in a normal fashion and needs and wants cushioning and
protection in a shoe.
If walking and running barefoot do not generally cause shin splints it follows
that there is a problem
with shoes.
Almost all running and walking shoes extend the heel rearward. It is customary
for the heel of the
shoe to extend downward from a point at the back of the wearer's heel plus the
thickness of the shoe
material often plus the welting. See Figure 3A. Many designs of shoes extend
even further
rearward. Even when the heel of the shoe is not extended rearward the strike
point is moved
rearward by the cushioning of the sole of the shoe. The strike point is far
back of where the bare
foot would strike.
In Fig. 3A, line 11-12 represents the lever arm the shin muscles pull against.
Line (12-18) represents
the counter lever arm of the calcaneus, which has body weight acting on it
through the tibia talus
joint. Line (16-18) represents the extension of lever arm caused by the heel
of the shoe. This
violates the natural amount of leverage the shin muscles work against when
suspending and
lowering the foot. It can easily be seen that the leverage working against the
shin muscles in this
shoe is nearly doubled and this is not at all an extreme example. Shoes and
boots that extend
rearward much more are common. According to experts the forces on impact can
be 3-4 times
(another ref says up to 11X) body weight. Extend the strike point of the heel
rearward and the
leverage ratio against the shin muscles is increased. The fairly conservative
extension of the heel in
Fig 3A increases the lever arm by almost 90%, almost doubling forces. A 200
pounder will go from
600-800 pound impact force to something approaching a ton. The shin muscles
are overpowered
and forced to extend by the impact and are damaged as a result. This is most
pronounced in
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activities like running or extended periods of walking where the repetitive
action eventually
damages the muscles and tendons of the shin area (bone damage can also occur
from repetitive
strain on the tendon attachments). People who land heavily or are overweight
will suffer more from
tendon strain.
An easy way to discover for yourself how this works is to put your bare foot
out in front,
toes up like you'd be landing on it while taking a stride. Push on your heel
with your weight and
feel the pull on the muscles of the shins. Next, put on your shoes and do the
same action and feel
the difference. You will feel the greatly increased pull on those shin muscles
especially if body
weight is applied as the forefoot nears the ground. They may not have the
strength to hold the toes
up.
Figs. 3A to 8A give examples of prior art that show this extension of the
lever arm over that which
occurs naturally.
It is this increase of leverage against the foot structure that causes the
slapping or clomping sound
of a walking shoe or boot that is often heard when the forefoot strikes the
ground/floor hard. This is
because of the shin muscles being over powered and the forefoot falling in an
uncontrolled manner.
This overpowering of the shin musculature is what causes the damage to them.
This is noticeable
shoes or boots with heels of poor design and hard soles. The sound is not
heard so much in softer
soled shoes but the damage to the body is still going on.
To increase cushioning the clearance between the foot and the sole must be
increased. It is the
function of cushioning to gradually decelerate the foot to remove the shock of
a sudden stop of the
foot hitting a hard surface. To have a more gradual deceleration the thickness
of the cushion must
be increased to have a greater range in which to accomplish the deceleration.
Any shoe design that raises the heel of the wearer needs to have the point of
heel strike adjusted as
any increase in height begins to move the strike point rearward of the natural
strike point. Even
barefoot type shoes with minimal thickness still make small additions to the
dimensions and thereby
to the lever arm of the actual bare foot. The wear layer of even this minimal
type of shoe will extend
the strikepoint of the heel rearward by its thickness¨a consideration for the
serious runner.
In a design where the contact point is relatively square as in Fig 3A the
pivot point is maintained at
the point of contact rather than moving forward as in a rounded heel. This
makes for the worst
lever disadvantage.
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PROBLEM 2: Millions of runners and walkers suffer from plantar fasciitis. For
some it is
controllable, for many it prohibits them from walking, running or even
enjoying life without pain.
Plantar fasciitis involves pain and inflammation of a thick band of tissue and
its connective points,
called the plantar fascia, that runs across the bottom of the foot and
connects the heel bone to the
toes, Fig. 1 (24, 25). Its function is to help stabilize the bones of the
foot. As one takes a step the
toes are raised which tightens the fascia by pulling it around the head of the
metatarsal bones (26) in
what is called the "Windlass effect". This pulls up the arch of the foot (also
referred to as a truss)
readying it to take the body's weight. This not only stabilizes the foot but
is another part of the
system to gradually accept the load while using the muscles and tendinous
tissues to absorb shock.
This cycle occurs as the forefoot touches down and gradually loads as the knee
passes over the foot
and allows full transfer of the body's weight.
The plantar fascia spans the five metatarsals and attaches to a single point
(24) on the calcaneus. In
fact it is the plantar fascia that plays a major part in holding the calcaneus
in place as it bears load.
An extended lever arm acting on the calcaneus, caused by shoe heel design will
overload the plantar
fascia. Most of the problems and pain in plantar fasciitis involve the
attachment of the fascia to the
anterior calcaneus, point (24). Heel spurs are a common malady. This is the
focal point of all the
loading of impact. The shin muscles suspend the front of the foot and toes.
The plantar fascia
connects this pulling force to the calcaneus.
This overloading of the calcaneus on the crucial point of contact lessens the
stability of the foot
structure and increases the likelihood of stride patterns deviating from the
norm. Problems with
weaknesses in structure will be magnified.
Another point which ties these two problems together is that the muscles
working to pull the toes up
in the "windlass effect are anterior shin muscles. Here again is direct
increased strain on those
muscles through the plantar fasciae when the strikepoint of the heel is
extended rearward.
There is a plethora of data available on how pronation, supranation, improper
arch heights and so on
affect gait and structure. It is easy to see how these conditions can be
exacerbated by overcoming
the stability of the foot at the beginning of the cycle with an over-leveraged
heel strike. The arch
itself is supported by the plantar fasciae, which in turn are acted upon by
the shin muscles.
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It is plain to see that extending the lever arm of the heel will directly
increase the forces acting on
the plantar fascia.
Extending the lever arm of the calcaneus causes overloading which damages the
fasciae, ligaments
and their connections to the bones. It is also notable that a large number of
those suffering from
plantar fasciitis are runners, those whose work involves walking and those who
are overweight.
Extending the heel and increasing the forces acting on the plantar fasciae of
an overweight person
greatly increases the probability of damage. The repetitive action of running
or extended periods of
walking magnifies the problems caused by increased leverage on the calcaneus.
Prior Art Figs. 3A through 8A give examples of the lever arm of the calcaneus
being increased by
shoe heel design.
PRIOR ART
Many prior designs have mentioned reduction of shin splints in their claims.
US patent 5,694,706,
Penka discloses a running shoe with the no heel, the object being to force the
wearer to land on the
forefoot thus ensuring the anterior muscles are not loaded, the entire weight
being handled by the
calf muscles. This may be a viable system if one chooses to walk or run in
this fashion.
This invention obviates the heel landing by design and does not interfere with
my design for that
reason.
US patent # 6,131,309, John Walsh mentions a need to correct abnormal
pronation which can cause
trauma, such as shin splints. His invention is a suspended heel carriage which
allows movement of
the heel and a different type of shock absorption. It does not address the
problem of unnatural heel
strike overloading the Medial tibial muscles and tissues or plantar fasciae.
US patent 4155180, Edward H Phillips¨Roller Shoe, discloses a design of
continuously rounded
(front to back) sole of running shoe. He states: the rearward portion of the
shoe is curved
upward... This shape functions to relieve the runner of his tendency to land
on his heel.. .thereby
relieving heel shock. This design may work but necessitates a very thick
rounded portion of shoe
sole and is not the choice of all. In this design the heel is still extended
rearward so that if one does
land on the heel there will still be an overloading of the shin muscles as
well as plantar fasciae.
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US Patent 7,100,307, Footwear to enhance natural gait discloses a design of
shoe with a round heel.
This patent does have a heel design similar to that laid out herein but per
drawings the radius of heel
is not maintained but rather enlarged which moves the strikepoint rearward,
increasing the lever
moment against the shin muscles. This design is for a specific shoe as well
and does not encompass
all forms of footwear. The patent does not make any claim as to the radial
design of heel in the
sagittal plane to reduce shin splints or plantar fasciitis.
US patent Rosa discloses a shoe with a somewhat similar heel design but does
not follow the
formula of maintaining the radius of the heel and strikepoint of the bare
foot. It in fact states the
primary point of contact is on the rearmost part of the shoe which increases
leverage against the
shin musculature. It also does not make any claim of reducing the incidence of
shin splints or
plantar fasciitis.
EP 2319344 Al by Stanislas Rio claims the risks of development of known
related pathologies from
the interaction of the foot heel and the footwear are minimized. His design is
for a heel suspension
and the heel of his design is conventional.
SUMMARY OF THE INVENTION
This invention has to do only with the rear part of the heel of an article of
footwear which is the
primary engaging unit in heel strike walking/running. The object of this shape
of heel is to obviate
the possibility of unusual shin muscle/ligament strain and plantar fasciae
strain by maintaining the
natural strike point of the heel of a bare foot. By maintaining the natural
strikepoint, the lever arm
of the heel and thus the loading is not increased.
This shape is only addressed in the sagittal view--that is fore and aft. This
point is below the curve
of the calcaneus bone at the approximate point it meets a parallel of the
bottom of the foot as in Fig.
1 point (14) and following the radius of the contact area (8), rearward on
inclination. This is the
radius the heel follows under weight. This radius is defined by the radius of
the calcaneus (7).
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DRAWINGS--FIGURES
Fig 1 shows a sagittal view of a bare foot on a horizontal surface, bearing
weight.
Fig 2 shows a sagittal view bare foot, inclined and contacting the horizontal
at approximately 200
.
Fig 3A shows sagittal view of a foot within a shoe, inclined and contacting
the horizontal plane.
Fig 3B is the shoe of Fig 3A with a modified heel.
Fig 3C is the shoe of Fig 3A with an example of another type of modified heel.
Fig 3D is the shoe of Fig 3A with a third type of modified heel.
Fig 4A shows sagittal view of a foot within a running style shoe, inclined and
contacting the
horizontal plane.
Fig 4B is the shoe of Fig 4 with a modified heel.
Fig 5A-8A show sagittal views of a foot within a shoe, inclined and contacting
the horizontal plane.
Fig 5B-8B show sagittal views of a foot within a shoe with a heel modified per
Detailed
Description First Embodiment.
Fig 5C is the shoe of 5B with a lower heel.
Fig 6C shows a variation of 6B which conforms with alternative embodiment 3C.
Fig. 8C is an alternative embodiment of 8B.
Fig. 9 shows an example of a heel in which the contact point can be adjusted
forward to reduce
loading on foot and appended structure in the case of weakness or pathology.
DRAWINGS¨REFERENCE NUMERALS
2. the calcaneus bone.
4. the talus bone
6. the tibia bone
7. the radius of the calcaneus which delineates the form of the heel.
8. the radius of the contact area which is the radius the heel follows under
weight. This is
approximately half the unloaded tissue thickness.
9. the radius of the contact area the heel follows under weight duplicated in
the heel of the shoe.
10. radius 7 extended into a circle to illustrate the use of the back of foot
as a marker for the
placement of radius 9 in the shoe heel.
11. represents the approximate point on the top of the foot the shin muscles
pull on¨shows the
point of leverage of the shin muscles.
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12. the approximate point the foot pivots on.
14. the contact point of the heel when the forefoot has touched the
horizontal. This point varies
with thickness of heel tissue and shoe material but is always perpendicular to
this point and is a
point on line 14.
15. the contact point of a heel moved anterior for the purpose of lessening
the load on foot structure
in the case of pathology thereof.
16. the approximate contact point of the heel of a foot inclined in relation
to the horizontal. About
200 in Fig. 2.
17. the point of contact of the foot were it to contact the horizontal at 45 .
18. the contact point of the extended heel of the shoe.
Line 11-12 represents the approximate lever arm of the shin muscles.
Line 12-14 represents the approximate lever arm of the calcaneus-talus under
load which is pulling
against the shin muscles and the plantar fasciae as the foot comes to rest.
Line 12-16 represents the approximate lever arm of the calcaneus-talus when
the foot is contacting
at an angle of 20 to horizontal.
Line 12-17 represents the approximate lever arm of the calcaneus-talus if the
foot were to contact at
an angle of 45 to the horizontal.
Line 12-18 represents the approximate lever arm of the calcaneus-talus when
the foot is contacting
through the extended heel of the shoe.
Line 16-18 represents the addition to the natural lever arm applied by the
shoe heel.
Line 14-18 represents the addition to the natural lever arm applied by the
shoe heel as the forefoot
contacts.
20. represents the horizontal plane or ground.
21. adjustable portion of shoe heel.
22. slotted area to allow adjustment.
23. screw fasteners.
24. attachment area of the plantar fasciae to the calcaneus.
25. the plantar fasciae.
26. head of the first metatarsal.
27. the rear profile of the heel of Fig. 3D.
28. represents the approximate area the shin muscles pull on to raise the
forefoot.
35. represents the horizontal (ground) if the heel meets it at a 35 angle.
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40. represents the horizontal (ground) if the heel meets it at a 400 angle.
45. represents the horizontal (ground) if the heel meets it at a 45 angle.
DETAILED DESCRIPTION--FIRST EMBODIMENT¨FIGS. 3B-8B
All embodiments of this design deal only with the shape of the heel in the
sagittal plane that is, the
side or profile view.
As seen in Fig. 1 the contact point of the radius of the heel when the foot is
flat on a surface is point
(14). This point is defined as the approximate point being vertically below
the point where the lower
posterior radius of the calcaneus (7) meets a parallel to the horizontal plane
of a foot supporting
weight on heel and forefoot. This point of the calcaneus meets the surface
through the padding of
the heel tissues and bears the weight of the standing body bearing on the
heel.
As seen in Fig. 2 the contact point of the foot when it meets the ground
surface at an angle is
described by radius (8). This is the radius of the contact area, which is the
curve the heel follows
under weight. This curve ends at line 14. This curve or radius is
approximately half the unloaded
tissue thickness. This can also be described as the radius of the calcaneus
plus approximately half
the thickness of the heel tissue. A workable measure for this radius is
approximately 14% of the
total foot length. This radius can be positioned on the shoe heel by using a
perpendicular aligned 0-
2% anterior to the posterior most portion of the wearer's foot. This is given
as a range because of
differences in individual person's heels. It is also fine tuning in comparison
to the gross additional
leverage caused by most shoes prior to this design.
This radius is brought down perpendicularly to the ground plane until its
lower part meets the
intersection of line 14 with the bottom horizontal plane of the shoe heel.
This can be further refined by using the intersection of this radius (9) with
a 45 plane as in figure
3B, line (45).
The 450 line from this intersection to the welt area of the shoe can be used
as the demarcation line
of the rear of the shoe heel, giving more space for material in the welt area.
Material anterior to the
45 line will not increase leverage against the heel. This also gives a clean
line to the back of the
shoe for esthetic considerations. The 45 angle is chosen as the likely limit
of inclination of the foot
on contact. It is well beyond the average but there are some that walk or run
in this manner.
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A further definition of this shape of shoe heel is that no material shall
extend posteriorly from the
area described by the lower part of the radius and above the intersection of
the radius and the 450
angle by that angle. This prohibition ensures no added leverage is applied to
the wearer's heel by
ground contact of the heel of the footwear. This definition can be changed to
suit the chosen
maximum angle of contact where it is determined that the maximum angle of
contact will be
different for shoes intended for a given activity. For example a jogging or
walking shoe or one
intended for someone with pathology could have a lesser maximum angle of
contact. A shoe for
certain sport activities may need a greater maximum angle of contact.
A heel of this design can be constructed with any of the various materials
used in heel construction.
The only requisite being that resilient type materials be of sufficient
firmness or of a design to resist
excessive deformation on contact that would move the contact point more than 1-
2% of the entire
foot length forward of that designated by point 14. If a fluid such as air or
gel is used as part of the
cushioning its confining structure must be such that will not allow deforming
of the given design
thus preventing the movement of the contact point forward or aft of that
designated. These
requisites are well within the knowledge and abilities of anyone knowledgeable
in the art of modern
shoe making and manufacture. Moving the contact point significantly forward of
point 14 will bring
the foot into a condition wherein the shin muscles having a lever advantage
will momentarily halt
the normal declination of the foot. This will cause a jolt, which is
transmitted up the leg. Further as
the body weight passes over the foot the shin muscles will then be overpowered
and the foot will
drop uncontrolled. Maintaining point 14 as the final contact point is the most
important point in
maintaining natural loading.
This design will work well with materials of little or no resilience such as
the relatively solid heel of
a boot or service shoe or dress shoe.
The design can be incorporated into attached or molded heels.
The point of contact and the radius of the contact area may be fine tuned to
meet the exact needs of
the wearer, for example in a shoe of one who does a lot of running or one who
has some pathology
or abnormality of the foot.
Each shoe in Figs. 3B through 8B show examples of the radial or rounded
design.
OPERATION¨FIRST EMBODIMENT¨FIGS. 3B-8B
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The point of final contact of the contact radius has been placed directly
beneath point 14 and is
defined as being that point of the radius of the calcaneus which meets with a
horizontal plane
parallel to that plane shared by the heel and forefoot of a weight bearing
foot. A workable average
measure is about 12% of the entire length of the foot forward of the rearmost
part of the heel as
shown in Fig. 1 . Making the heel of the shoe match the shape of the actual
heel under load Fig. 1,
radius (8) gives the best match to the natural strike zone of a bare foot.
(Note: the center point of
the calcaneus and the heel radius under load is forward of point (14) see
circle (10). This is an
important point in bringing the radius down in the shoe heel so that it is not
placed too far back, as
would be the case if the radius were aligned with the center perpendicular to
point 14. If the radius
of the wearer's (person's) heel under load is extended into a full circle (10)
it can be seen to closely
align with a perpendicular, generally about 0-2% of entire foot length forward
of the back of the
wearer's heel, Fig 1. This makes that perpendicular a useful orientation point
in aligning the radius
on the shoe heel.)
Use of a round contact area provides a more gradual loading. This also has the
effect of dissipating
forces over a larger area. The result of placing the contact point in this
manner is no excess strain
on the shins, no excess loading of the plantar fascia and a very nice
lightness and smoothness to the
impact of each step. This keeps all the forces generated by the heel strike
landing in a range the
body is naturally designed to cope with.
Use of the round contact area also allows the use of more material which will
tend to hold the given
shape better under load so that the contact point is not moved forward of
point 14 under load.
As seen in Fig. 6B and 6C the design is easily applied to a heightened heel.
As seen in Fig. 5C the design works with a relatively low heel as well. With a
low heel it is
especially important to ensure the rear welt area is free of material that
could contact the ground on
heel strike.
DETAILED DESCRIPTION¨ALTERNATIVE EMBODIMENT Fig. 3C.
One can simply use point 14 as the strikepoint as has been borne out in
testing. Fig 3C shows the
shoe heel is simply cut off at point 14 as seen in the sagittal view.
OPERATION¨ALTERNATIVE EMBODIMENT Fig. 3C.
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14
This shape has been tested and has been found to give similar comfort and ease
of stride with no
strain on shin muscles. It will slightly alter the natural loading cycle
making it less gradual than
with a rounded heel. This could possibly cause more strain on certain muscles
after many strides as
in distance running. It works fine with harder materials but likely not hold
its shape as well with
resilient materials. It is not an esthetic design and would likely look odd or
suspect to the average
consumer. It would also be subject to wear moving the contact point forward
much more quickly.
One could make almost any shape work in this embodiment as long as it has
point 14 as the contact
point, has no material posterior to the 45 angle or chosen maximum angle and
supports the weight
of the wearer.
DETAILED DESCRIPTION¨ALTERNATIVE EMBODIMENT Fig. 3D.
Fig. 3D shows the shape of the rear of the shoe heel is simply a straight line
from pt.14 to the welt
area of the shoe (27) as seen in the sagittal view. This design adheres to the
rule of no material
posterior to that shown in Figure 3B. The shape in this embodiment can also be
varied as long as it
has point 14 as the contact point, has no material posterior to the 45 angle
or chosen maximum
angle that will contact the ground and supports the weight of the wearer.
OPERATION¨ALTERNATIVE EMBODIMENT Fig. 3D
This shape has been tested and has been found to give similar comfort and ease
of stride with no
strain on shin muscles. This shape is a compromise between the round design of
Fig3B and the
square of Fig.3C. It gives similar advantages to the square cut design, will
wear better, deform less
with resilient materials and will look more acceptable to the average
consumer. It is extremely
simple to shape, mold or cut.
DETAILED DESCRIPTION¨ALTERNATIVE EMBODIMENT Fig.8B.
Fig. 8B shows a runner with a resilient shock absorbing member(s) between the
upper outsole and a
leaf member meeting with the supporting surface (ground). The leaf and shock-
absorbing member
are curved in accordance with the design at the rear, the curve beginning at
pt. 14. The curve is cut
CA 02831318 2013-10-30
short of the bottom of the shoe to allow compression of the shock-absorbing
member. The bottom
member can also be formed as simply as ending its length at point 14.
OPERATION¨ALTERNATIVE EMBODIMENT Fig.8B.
This design gives the same advantages of maintaining the contact area of a
bare foot that is given by
the round heels of the 3B-7B series while allowing the use of cylindrical
shock absorbing members.
These shock-absorbing members could also be replaced by coil springs of a
similar size. This
particular design would have 2 shock absorbing elements side by side. Only one
is seen in the
sagittal view. A similar design could be made with a single or pluralities of
shock absorbing
member and or spring(s).
This design may also be formed of a leaf spring, which forms the lower leaf
and is incorporated into
the upper outsole, Fig 8C. Said leaf spring design could also incorporate any
of the shock absorbing
and coil springs elements described above.
DETAILED DESCRIPTION---ALTERNATIVE EMBODIMENT Fig. 9
As it is the musculature of the shin area that suspends the forefoot and takes
up some of the
force of impact as well as controlling the fall of the foot, it may be found
that for therapeutic
purposes in cases of weakened or damaged musculature the strike point may be
adjusted forward of
the natural point to compensate for such weaknesses. That is a heel contact
point formed anterior to
point (14) or a heel with an adjustable contact point that can be designed to
adjust for that purpose.
Thus effectively shortening the lever arm of the heel of the wearer. This may
be applied to Plantar
fasciitis and related conditions as well.
OPERATION¨ALTERNATIVE EMBODIMENT Fig. 9
This moving of the contact point forward can be attained by simply cutting or
molding a special
shoe heel with the contact point moved forward to a degree suited to the
individual.
A variation of adjustable strike point heel can be made in which the strike
point is adjustable
for the exact need of a particular person and then moved rearward toward the
natural strikepoint as
that person's pathology reduces. Thus allowing the structure of the foot to
gradually strengthen and
attain normal function.
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16
In Fig. 9 the lower portion of the shoe heel is a formed as a separate piece
(21). It is
attached to the main body of the shoe by screws (23) which are located in
slotted channels (22) to
allow adjustment forward and back. This allows the main contact point, (14a
when moved), to be
adjusted forward of the normal strikepoint (14).
In adjusting the strikepoint forward it is necessary to adhere to the rule of
no material
projecting to the rear which will increase heel leverage at any point of the
heel strike. In designing
this heel and the shoe it may be determined that one who has a foot pathology
may not need the
room for a great deal of inclination on contact. For example a person with
chronic shin splints may
only need a maximum inclination of 300 on heel strike which will allow more
clearance for material
at the rear of the shoe.
CONCLUSIONS, RAMIFICATIONS AND SCOPE
The reader will see that applying this design of shoe heel to any footwear
design will allow the
wearer the advantages of cushioning, protection and esthetics given by
footwear without the
damaging effects of poor heel design. If one considers the size and weight of
a body in comparison
to the size and structure of the ankle and heel it is easy to see that a small
member carries a large
load. This load is magnified greatly in running. As this structure has been
formed over ages of
evolution it is therefore deemed of proper design by survival alone. One
should take great care
before introducing modifications to the operation of the foot.
Fig. 2 shows the lever arms of the calcaneus and the supporting shin muscles
and Fig. 3A the
extension of the calcaneus lever arm given by a common shoe heel. It is very
simple to see that any
shoe heel that extends this lever arm upsets a balanced system. This will
result in damage to that
system¨minimally to the shin muscles, the plantar fasciae and their
attachments.
Maintaining the natural contact radius of the heel as in Fig. 3B will not
upset the balance of the
natural system and will not cause undue damage to the components of that
system. Just being
relatively close in design to that set out herein will keep most feet in a
tolerable range of stress.
This design can be applied to any footwear. The design allows the use of
cushioning without
changing foot leverage. Even a flip-flop sandal increases the leverage of the
calcaneus structure by
the thickness of the sole wrapping around the heel with each stride. One could
even walk with
grace in a platform boot if the heel were cut to this design.
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It is not contemplated that there is any material or type of heel or heel
cushioning or suspension
currently used that couldn't be used while conforming to this design. In
heightened heels the
contact area of the heel need only conform with that set out herein and the
same advantages will be
realized. No special manufacturing techniques are necessary, only the shapes
of molds or cuts of
material need be changed.
The wearer of footwear with this heel design will instantly realize an ease of
motion and gait similar
to walking barefoot.
This improvement on design of a running shoe or walking shoe or boot for that
matter will prevent
or greatly lessen the problem of shin splints and or plantar fasciitis for
most and alleviate the
problem for those who already suffer from shin splints/plantar fasciitis. This
concept can be carried
further to any other type of footwear. The more one walks the more important
the point of heel
strike becomes. Also the heavier the person, the more important this point of
correct leverage in
footwear.
It is also an important consideration for one with any of the various foot
pathologies. It would be
proper to correct the strikepoint of the heel before addressing other foot and
related pathologies. It
is quite possible that many other foot pathologies arise from the excess
forces caused by increased
leverage on the heel at contact.
NB. The strikepoint is referred to as point 14. Radius 8 is the preferred
strikepoint. This is the
radius formed by the progression of the strikepoint from first contact at the
maximum inclination of
that contact to the point it meets the horizontal that being point 14. Radius
8 does extend the
strikepoint rearward as it comes into contact with the ground but the foot
does not support a great
deal of weight during this part of the stride unless the person moves in a
very clumsy manner in
which case it is even more important to not extend the strikepoint rearward.
It is important to
understand that in a bare foot the contact point moves forward as the heel
contacts and rolls forward
until the foot is fully contacting. This forward movement of the contact point
increases the lever
advantage of the supporting shin muscles as the body weight borne by the foot
increases with
forward motion. This allows the shin muscles to do their function of
supporting and controlling the
suspension of the rear foot as well as absorbing some of the shock of impact.
As long as this natural
progression of leverage is not interfered with a healthy body is not unduly
plagued by shin splints.
14% of overall foot length as the radius of the heel is a workable estimate of
a normal average. It
could be slightly more or less depending on the individual. If one looks at
the difference this makes
in leverage it is seen to be minor when compared to the gross additions to
leverage caused by shoe
heels that do not conform to the measures of the wearer's foot itself.
CA 02831318 2013-10-30
Patent Application of
Larry Macdonald
for
Footwear heel designed to prevent additional forces acting against the
wearer's heel
caused by the footwear. The intention of the design being to alleviate shin
splints, plantar
fasciitis and associated medical problems caused or worsened by said
additional forces
and to promote ease of gait and grace in heel and toe walking/running, that is
bipedal
locomotion wherein the strikepoint of the leading foot is the heel.
Footwear heel design to allow natural movement of foot in heel and toe /
walking
running.
Use of heel design to alleviate a medical condition of the foot, specifically
shin
splints/plantar fasciitis.
Cross reference to related applications: NA
In this paper shoe and footwear are used interchangeably.
Sagittal plane refers to the plane of the side view of the body, profile is
also used with the
same meaning.
Heel in reference to footwear means the ground contacting rear portion of an
article of
footwear, that portion which supports the heel of the wearer.
Ground refers to the surface being tread upon.
Stride cycle refers to the motions gone through by a foot and leg in bipedal
locomotion,
walking or running.
