This
subject demonstrates a well co-ordinated and
very smooth movement from standing into sitting.
The movement goes as follows:
The
head tilts interiorly so that the face is directed
obliquely downwards. At the same time the hands
are placed on the waist and the right foot slides
posteriorly so that the right knee bends very
slightly. This carries the body weight posteriorly
to fall between the two feet and increases the
anteroposterior dimension of the supporting base – thus
preparing the subject to be able to control the
balance during the next stage of the movement.
The
subject then lowers the pelvis onto the stool
very slowly to a count of four evenly spaced
intervals. As this occurs, the pelvis rolls forward
over the hip joints and the left lower limb takes
up a right angle at the knee whilst the right
lower limb is more acutely flexed and the foot
is posterior to the knee, but anterior to the
coronal plane of the body.
Finally,
the right foot slides forward to lie immediately
under the right knee and so makes the knee adopt
a right angle. At the same time the pelvis rolls
posteriorly to become upright over the hip joints
and so creates a right angle between the pelvis
and thigh. Concurrently, the head regains the
normal upright posture. The hands are still on
the lateral aspect of the waist and the whole
action has occurred completely smoothly. |
This subject demonstrates poor control
of the movement and associated balance reactions.
The movement is as follows: The head tilts forwards
in the same way as Subject A and the hands are placed
on the lateral aspect of the waist. However, there
is no adjustment of the feet to make the anteroposterior
dimension of the base more suitable and the knees
remain straight with the weight passing evenly between
the feet which are both immediately under the body
and in alignment with its coronal plane.
The subject then remains poised like this for
three evenly spaced intervals and then suddenly
drops the pelvis onto the stool, virtually collapsing
at the knees and hips. The ‘landing’ is
noisy and sudden, no balance adjustment of the
trunk occurs and the body does not incline anteriorly
at the hips.
Finally, the head is tilted posteriorly on the
trunk momentarily before being adjusted to the
normal upright posture. The final posture is identical
to that of Subject A, but the method of attaining
it is much more hazardous and traumatic.
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