In view of all the comments on the use of shoes in sport, here are some
extracts from our 'Supertraining' book (Siff & Verkhoshansky 1999 Ch 8) that
are relevant to the discussion.
Later I have provided a collection of websites that will also shed some more
light on this issue.
SHOES AND SAFETY
Shoe manufacturers would have athletes believe that the primary solution to
most athletic 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 and that current athletic footwear may even be injurious
(Robbins et al, 1988). The paradoxical observation of a much lower incidence
of running injuries reported in barefoot populations implies that modern
running shoes may produce injuries that normally would not occur without
their use (Robbins & Hanna, 1987). Furthermore, running shoes seem to be
associated with fewer injuries in fitness classes than so-called 'aerobics
shoes'. Nigg (1986) 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
(Robbins et al, 1988; Clarke et al, 1982). Similarly, epidemiological
studies have failed to provide evidence that expensive modern athletic
footwear enhances protection from injury to the lower extremities (Caspersen
et al, 1984; Powell et al, 1986). Thus, it would appear that safety of the
lower extremity is not simply a consequence of suitable footwear, but of
learning how to move the body efficiently while wearing a specific type of
shoe.
SHOE DESIGN
Clearly, the science of athletic shoe design is far from being exact. For inst
ance, the current fo-cus is on foot pronation. Other possible causes of
injury such as toe, ankle, knee and hip movement in three dimensions are
largely neglected. Moreover, footwear design is based almost exclusively on
theoretical models which postulate that shock loading and the inability of
the human anatomy to adapt to this loading are the primary causes of running
injuries. This becomes evident from the claims of manufacturers that their
specific shoes correct excessive pronation, control the rearfoot, offer
superior arch support or absorb shock effectively. These shoes do not modify
the impact forces during locomotion, a fact which casts severe doubt on the
cushioning philosophy that forms the foundation of all current shoe design.
Studies by Robbins et al (1988) have shown that the sole of the bare foot
exhibits a powerful plantar surface protective response which diminishes
plantar loading on ground contact, thereby reducing the risk of damage from
overloading during locomotion. Their work also revealed that this response
was not apparent among subjects who always wear shoes, especially the highly
shock-absorbing shoes generally worn by runners. They concluded this
protective response prevents injury by decreasing system rigidity, thereby
diminishing the peak force during foot impact. The lack of the protective
response among shoe wearers apparently is due to diminished plantar sensory
feedback, possibly combined with mechanical interference with arch deflection
by shoe laces, heel counters and arch supports (Robbins et al, 1988). It
would seem that sufficient regular locomotor activity without footwear should
be done daily to maintain the sensitivity of the plantar protective reflex
and that less emphasis should be concentrated on designing passive
shock-absorbing or pronation-modifying shoes.
Little work has been done on relating lower limb injury to anthropometric
factors such as bodymass, height or limb length, or other factors including
level of qualification, movement intensity, muscle fibre distribution,
patterns of EMG activity, feedback processes or bone density. No research
has examined aerobics or 'cross training' shoes with this degree of
thoroughness, nor has it carried out entirely satisfactory three-dimensional
studies of all physical factors influencing the efficiency of whole body
movement from initiation to termination of a locomotor action, in particular
with respect to the optimal design of any shoe.
Irrespective of how well designed shoes are, they must be used correctly in
different move-ments. In doing so the user must be aware that shoes always
reduce the proprioceptive and tactile sensitivity to the surface on which
they are being used.
Another reflex is also worthy of attention. 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 (see 3.5.3), which normally
operates highly effi-ciently in bare feet to produce strong reflex extension
of the legs and stabilisation of the body, is delayed in facilitating rapid
cybernetic control and correction of unsafe movements when shoes are worn.
In particular, the locus of application of pres-sure to the surface of the
sole of the foot determines the position to which the limb will extend
(Guyton, 1984), so that inappropriate geometry of the shoe can significantly
alter the pattern of recruitment of the muscles of the lower extremities.
In contrast, the use of bare feet on firm, very high density chip-foam mats
in the average fitness class preserves proprioceptive efficiency, lowers the
centre of gravity of the body and, unlike shoes, does not increase the lever
arm length from the point of heel contact to the ankle joint, thereby
reducing the moments of force about all joints of the lower limb.
If anyone is interested in the biomechanics of shoe design and use, the
following book is very informative:
Nigg, B The Biomechanics of Running Shoes 1986
There are several useful websites on gait analysis and footwear that are also
relevant. Here is a small sample of ones that you might enjoy:
barefooters.org/medicine/med_sci_sports_exer-23.2.html (Barefoot Running)
barefooters.org/medicine/ (Bare feet are healthier)
uni-essen.de/~qpd800/FWISB/sneakers.html (Footwear Biomechanics)
ortho.rush.edu/gait/cases1.htm (Gait Analysis - Educational site)
polyu.edu.hk:80/cga/ (Clinical Gait Analysis)About the Author:
Dr Mel Siff Author of Supertraining + Facts and Fallacies of Fitness http://www.drmelsiff.com