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M Swanepoel
04-20-1998, 06:04 PM
Hello Biomekkers,

I agree with Margrit Meiers of Sherbrooke: Slowing of walking speed
upon ageing is a multi-faceted phenomenon, and concentration on the state
of the lower limb joints alone is not going to provide the full
picture. Walking is of course an incredibly complex motion with
great involvement of the cerebellum and the semi-circular canals of
the ear. Furthermore unconscious arm motion takes place in order to
provide a properly balanced action, and the state of the spine may be
important.

The elderly certainly find it more difficult to retain their balance, and this seems
to be related to otolithic and proprioceptive function. (If anyone out there
conducted the classic standing tests on a force plate, please write
in!) Furthermore there is an extreme awareness in the UK of the
possible consequences of femoral head fractures, so that there is
considerable fear of tripping over uneven paving stones and slipping
on ice, which can be very difficult to see. (Even the role of deteriorating eyesight
cannot be ruled out!)

Fibrosis and calcification of the intervertebral disks greatly decrease its
flexibility, and the spine usually ends in a slightly "stooped forward" position.
This brings the centre of gravity forward with respect to the hips,
and naturally makes it more difficult for afflicted individuals to
control their balance - hence they would walk more slowly.

Furthermore an interplay between loss of lumbar lordosis and the
role of the iliopsoas muscle bundle seems likely. Movement of
this region of the spine with respect to the hips would afford
iliopsoas less distance through which to act, which suggests that any
role it exercises in controlling the relative position of the trunk and limbs
would be compromised, exacerbating balance.

I know that Dr James Smeathers (Queensland Univ of Technology, Oz) showed
that the vibration damping characteristics of the spine vary considerably with
its state. (Impulsive loads travel more sharply through spines
with calcified and calcifying intervertebral disks, to the base
of the skull, presumably exercising a deleterious effect on spinal
joints.) Thus slow walking might have a protective function in this
regard.

What part/s of the gait cycle is/are in fact slowed, and are heel strike and
toe-off forces reduced in the elderly when normalised against
bodyweight?

Further, does anyone have data connecting walking speeds to diagnosed
conditions of the inner ear? (Send replies to the biomech group.)

Thank you.

Mark W Swanepoel
University of the Witwatersrand
South Africa

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