Here is an extract on the biomechanics of the foot and shoe
safety from Dr Mel Siff’s (www.drmelsiff.com) book “Facts and Fallacies of Fitness” (2000).
More of Mel Siff brilliant work, and those who are continuing it at http://health.groups.yahoo.com/group/supertraining
SHOES AND SAFETY
Shoe manufacturers would have us believe that the primary solution to most
Aerobics or running injuries is the wearing of expensive footwear. Ailments
such as shin splints, iliotibial band syndrome and peripatellar pain are
attributed variously to excessive shock loading of the limbs, pronation or
supination. Research, however, reveals that fewer injuries occur among
those who wear thin soled shoes or no shoes at all, even though the heel
strike forces are greater.
Furthermore, running shoes seem to be associated with fewer injuries in
fitness classes than so-called ‘aerobics shoes’. Nigg, in his book “The
Biomechanics of Running Shoes”, reports that on firm shock absorbing mats,
the difference in heel strike force is minimal between bare feet, thick-soled
shoes and thin-soled shoes. Nigg also points out that the use of any shoe
usually increases the tendency of the foot to pronate, particularly if the
impact forces are smaller.
Moreover, several studies have shown that there is no correlation between the
amount of shoe cushioning and impact absorption by footwear during
locomotion. Similarly, other research has been unable to provide evidence
that expensive athletic footwear improves protection from injury to the lower
extremities. The following references address these issues:
Caspersen C et al (1984) The incidence of injuries and hazards in
recreational and fitness runners Med Sci Sports Exerc 16: 113
Clarke T et al (1982) The effects of shoe cushioning upon selected force
and temporal patterns in running Med Sci Sports Exerc 14: 144
Powell K et al (1986) An epidemiological perspective on the causes of
running injuries Phys Sports Medicine 14: 100-114
Robbins S & Hanna A (1987) Running related injury prevention through
barefoot adaptations Med Sci Sports Exerc 19: 148-156
Robbins S, et al (1988) Overload protection: avoidance response to heavy
plantar surface loading Med Sci Sports Exerc 20(1) : 85-92
Shoe Design
Clearly, the science of athletic shoe design is far from being exact. In shoe
design, the current focus is on foot pronation Other possible causes of
injury such as toe, ankle, knee and hip movement in three dimensions are
largely neglected.
Little work has been done on relating lower limb injury to structural and
functional factors such as body mass, height or limb length, level of motor
skill, balance between muscle groups, patterns of EMG activity or bone
density. No published work has yet examined aerobics shoes with this degree
of thoroughness. Nor has it been able to carry out entirely satisfactory
three-dimensional studies of all physical factors which influence the
efficiency of foot movement from initiation to termination of movement and
then relate it to the optimal design of any shoe.
Pronation or Supination?
In particular, the actions of pronation and supination are invariably
oversimplified. Little is said about the orientation of the foot: whether it
is in a neutral, internally rotated or externally rotated position is not
mentioned when injuries to the lower extremities are analysed. Sometimes,
pronation is regarded as a synonym for inversion and supination as a synonym
for eversion, or even vice versa.
The distinction between these terms is vital to the scientific understanding
of foot mechanics and shoe design. Pronation of the foot refers to inward
rolling of the foot with weight being transferred more to its inside edge.
Supination refers to outward rolling of the foot with a transfer of more
weight to its outside edge. Both of these terms refer essentially to
rotation about a single axis, i.e. a two dimensional activity which can be
described completely by two numbers in mathematical space.
Inversion is a complex movement comprising simultaneous internal rotation of
the leg, plantarflexion and supination. Conversely, eversion is a
combination of external rotation of the leg with dorsiflexion and pronation.
In other words, these movements involve rotation about three mutually
perpendicular axes.
Since walking, running, aerobics and numerous similar activities involve the
foot in rapid three dimensional actions in space and in contact with the
ground, inversion and eversion can be seen to be the most appropriate factors
to examine if lower limb efficiency and safety is to be ensured. It is
inaccurate and seriously oversimplistic to rely on two dimensional
pronation-supination models of lower extremity injuries.
A three dimensional approach immediately identifies three major factors which
may be responsible for inefficient foot mechanics:
* the degree of internal/external rotation of the leg about the knee and the
lower extremity about the hip
* the degree of plantarflexion or dorsiflexion of the foot
* the degree of pronation or supination of the ankle.
As shoe design is not concerned primarily with what the lower extremity does
in free space, the magnitude of the above factors is most relevant while the
foot is in contact with the ground.
Shock absorbing soles, wedges and various orthotic devices are able to modify
significantly the degree of pronation or supination, but do not have a major
effect on the first two factors. Before purchasing a special shoe or
orthotic device, one should determine by careful biomechanical analysis which
of the three above factors are contributing most strongly to a particular
individual’s problem.
The problem may have little to do with excessive pronation or supination. It
may be concerned with one or both of the other factors as well – and these
are influenced dominantly by exercise technique, a neuromuscular phenomenon.
In other words, an improvement of movement skills, with or without a special
shoe, may be the best solution to foot-strike injuries.
Irrespective of how well designed shoes are, they must be used correctly in
different movements. In doing so the user must also be aware that shoes
always reduce the proprioceptive and tactile sensitivity to the surface on
which they are being used. Forces exerted on the shoe are delayed in being
transmitted through its shock absorbing sole en route to the foot. The reflex
positive supporting reaction which normally operates highly efficiently in
bare feet, is impaired in providing rapid cybernetic control and correction
of unsafe movements when shoes are worn.
The use of bare feet on firm, high density chip-foam mats preserves the
proprioceptive efficiency and lowers the centre of gravity of the body,
thereby reducing the moments of force about all joints of the lower limb.
Since the average commercial fitness centre is unlikely to encourage the use
of bare feet for reasons of appearance or cleanliness, it would probably be
more appropriate to recommend wearing soft ballet-type pumps or gymnastic
shoes in aerobics classes held on sprung wooden floors or very high density
chip-foam matting.
Arch Support
Some authorities recommend the use of special arches or shoe inserts to
absorb reactive landing forces and attenuate stress to the ankles, knees,
hips, back and body in general.
However, books such as Nigg’s “Biomechanics of Running Shoes” and
publications by S Robbins (Med Sci Sports Exerc 1987, 1988), point out that
the natural shock absorption capabilities of the foot may be severely
compromised by various arch and foot supports. In fact, these and other
publications reveal that there is a greater incidence of lower extremity
injuries among those who wear soft shock absorbing shoes (Some of this
research is summarised in Siff , “Supertraining” 2000, Ch 8).
Shock absorption by the bare foot is a very clever process which involves at
least the following passive and active methods of control:
* the foot arch is flexible like the leaf springs in many cars and is meant
to sag to absorb vertical shocks passively
* the connective tissue-linked matrix of various small bones in the feet is
meant to splay outwards to offer further passive shock absorption
* the skeletal structure of the foot and ankle allows the foot to ‘roll’ and
‘sag’ along its full length to distribute loading from heel to toe, thereby
offering another dynamic cantilever-like shock absorbing mechanism
* the tendons from the toes continue up the lower leg as part of the various
leg muscles and they change tension under neuromuscular control to offer
active control of impulsive loading
Firm arch supports, tight laces, highly resilient soles and relatively
inflexible soles tend to decrease the leg’s natural shock absorbing
capabilities and compel higher structures in the body, such as the knees,
hips and back, in order to cope with the shocks of landing. The thickness
and mechanical composition of the sole also slows down the ability of the
body to react to pressure on the soles of the feet, thereby compounding the
problem. In other words, in many cases, some “preventative” measures may do
exactly the opposite of what is intended.
……etc.
—————-
Mel Siff
http://www.melsiff.com
Mel Siff
Author of Supertraining
Author of Facts and Fallacies of Fitness
www.melsiff.com
Article Source: http://www.articlealley.com/http://melsiff.articlealley.com/dr-mel-siff-talks-safety-and-wearing-shoes-953488.html
Running injury; any possible remedies/precautions?
I recently started running about 3 miles a day. I’ll run one day at the gym on the treadmill when I lift and on days I don’t lift, I run on an asphalt track built around a lake nearby. My right big toe seems to balloon up, turns red/purple and pains me to a limp after a run. The next day it gets substantially better to the point where I can run again, but it still hurts a bit. The pain in between is substantial, sometimes, to the point where I can’t concentrate on what I’m doing. I really enjoy running and have no plans to digress. I have a 4 month old pair of Nike Shox that are broken in well, if that makes a difference. Please let me know if you have any suggestions on remedies or precautions I should take as I am new to running.
Answer
I’m an avid outdoor and treadmill runner and I can tell you that Nike Shox are not considered a running shoe. Go to any running store and most likely will not carry Shox. I have a pair of Shox and use them when lifting weights or wearing them outside. I love the way they look but I know the toe compartment in the shoe is compact.
My advise is to go to a running store and have them fit you for a 2 or 3 different pairs that they recommend. You choose the pair that feels the best to you. They can tell by looking at your feet whether you may have issues (such as under pronate, over pronate, etc) All of these can be corrected with the proper running shoe and the proper fit.
Some running stores have a treadmill in the store and they offer “gait analysis” so they can watch your form while you run.
I over pronate and this has been corrected by a pair of Brooks Addiction 7′s.
Since you are at a gym, try to also cross train on Elliptical and Stairmaster. Both are excellent cardio machines.
In closing, Runners World has an EXCELLENT online site that deals with topics like injury prevention and training programs. They even have a great listing of running shoes.
Good Luck!
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