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Humnfell
09-25-1998, 02:12 AM
On Fri, 25 Sep 1998 08:29:10 +0200 Juan Vicente Dura Gil
wrote:
> Dear biomechanics,
>
> In same cases, we have observed two small peaks at heel strike in the
> vertical force (measured with forceplatform). This two peaks appears
> with normal people in normal gait.
> I have done a literature review, and only one small peak is referenced.
>
> Someone has observed two small peaks at heel strike?
> Do you know any reference where two small peaks appear at heel strike?
>
> Thanks in advance
> --
> ************************************************
> Juan V. Durá - Instituto de Biomecánica de Valencia
> http://www.ibv.org
> Tel. +34 - 961366032 Fax. +34 - 961366033
>
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Dear Juan,

With regards to your problem, Dickinson et al. (Journal of
Biomechanics, 18, 415-422, 1985) have observed what was believed
to be an oscillatory type of shock wave when heel strike was
forceful, when running bare-foot. Alexander et al. (Journal of
Zoology, 209, 405-419, 1986) have stated that in animals, paws
with elastic pads tend to oscillate up and down after hitting the
ground. They might lose contact with the ground one or more times,
before settling on the ground at the beginning of a step: such
behaviour is called 'chattering'. However it has been reported in
Nigg et al. (Biomechanics of Running Shoes, 139-159, 1986)that
even some athletic-shoe combinations have double impact peaks for
running. The occurence of the two impact peaks is possibly caused
by either an impact type landing of the fore-foot (not rolling
movement)or a lateral slapping of the fore-foot (See Nigg,
Biomechanical Aspects of Sports Shoes and Playing Surfaces, 1983).


>From my own experience, double impact peaks were evident in heavy
pounders, i.e. runners who landed with high impact forces.
Similarly in certain runners, when landing bare-foot, a lound slap
can actually be heard. Centre of pressure data tends to indicate
that the second impact peak is explained by a slapping of the
fore-foot rather than the possible oscillatory motion of the
axial skeleton.

Regards,

Neil Fell
Post Graduate Researcher
Research Institute for Sport and Exercise Sciences
Liverpool John Moores University
HUMNFELL@LIVJM.AC.UK

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