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Victoria Haehl
02-24-1997, 01:56 AM
Following is a summary of the responses I received to the following question:

I am hoping to gain some insight into what (if any) is the difference
between postural control and movement control.

I have a difficult time believing that a dichotomy really exists. There
is movement control and coordination of the head, trunk, and pelvis. But
these segments are involved in movements, they are not fixed (the goal is
not always stability but coordination). There is some orientation towards
vertical, a tendency to keep our center of mass within our base of
support, and orientation of segments with respect to the task, but is that
a separate system? Aren't these the goals of most movements not just
postural control?
I have received 14 responses to date. Seven respondents thought there
was no difference between movement control(mc) and postural control(pc).
Five felt there is a difference, and 2 did not take a clear stand.
Certainly the way I phrased the question may have influenced the types of
responses I received. I was and remain interested in getting a variety
of viewpoints. I am encouraged by the lively discussion that this is an
interesting question. Below is a brief summary of the responses,
followed by a list of references provided by the respondents. I will
briefly restate some of the key phrases from the responses.

Those who believe there is a dichotomy:
THe dichotomy lies in the degree of conscious recognition
involved. THe goal of posture is not to move and is at a passive
sub-conscious level of control. Movement is defined as intentional
translation. Movement control strategies are deliberately planned and
executed.
THe importance of the neurophysiological perspective must also be
considered. Separate supraspinal, spinal, as well as vestibular
mechanisms control postural reactions (vs mc).
Clinically, one sees the need for stability before controlled movement.

THose who believe there is not a dichotomy:
THe distinction between mc and pc is arbitrarily a function of
facilitating research in movement control. The dichotomy exists for
academic convenience.
Postural and movement share effector organs, some neural
structures, and the equations for motion are the same . Pc and mc cannot
be processed separately. THey are not separate systems.
Movement and postural control are one in the same. It may be
useful to look at the body from a different mechanical perspective.
Instead of viewing the body as a system of pulleys and levers, biological
systems are tensegrity structures deriving strength from the entire
unit. These structures expand and contract around a 'neutral position'.
Lambda model discussed- simulation for motor tasks and for
postural stability using the same control variables gives the opportunity
to study mc and pc from the same point of view, linking neurophysiology,
mechanics, and physics.

Other thoughtful ideas:
THere is no such thing as a distinct control system to orient the
body with respect to balance. However, there is perception of
orientation, and to some degree, depending on the task, postural stability.
There is a lack of consistency in using terms and measures of
balance, stability, postural control... Perhaps these are not
quantifiable parameters.

Thank you all for your time and thought in responding to the question. I
received much food for thought and look forward to continued discussion.
Anyone who would like to continue the discussion, please feel free- I
will be here.

Sincerely,
Victoria Haehl
Indiana University
Dept of Kinesiology
HPER 112
Bloomington, IN 47405
(812) 855-3061
vhaehl@indiana.edu

References:(some are not complete and they are arranged by order of
response, not alphabetized)

Riccio, G. E. (1993). Information in movement variability about the
qualitative dynamics of posture and orientation. In K.M. Newell % D.M.
Corcos (Eds.), Variability and Motor Control (pp. 317-357). Champaigne:
Human Kinetics Publishers.

Riccio, G.E., Martin, E.J. & Stoffregen, T. A. (1992). THe role of
balance dynamics in the active perception and orientation. Journal of
Experimental Psychology: Human Perception & Performance, 18, 624-644.

Riccio, G.E. & Stoffregen, T. A. (1988). Affordances as constraints on
the control of stance. Human Movement Science, 7, 265-300.

Riley, M. A., Mitra, S, Stoffregen, T.A. & Turvey, M.T. (submitted)
Influences of body lean and vision on postural flucuations in stance.
Motor Control.

Stoffregen, T.A. & Riccio, G. E. (1988) An ecological theory of
orientation and the vestibular system. Psychological Review, 95, 3-14.

Berg, 1989
Dettmann et al., 1987
Goldie et al, 1989
Ekdahl et al., 1989
Mizrahi et al., 1985

Laquaniti, F., Maioli, C. (1994) Independent control of limb position and
contact forces in cat posture. Journal of Neurophysiology, 72, 1476-1495.

Hunt (1920, 1923)
Lawrence and Kuypers, 1968
Magnus, 1926
Beritoff, 1915
McNally and Tait, 1925
Martin, 1965
Suzuki and Cohen, 1964
Massion, 1984
Allum, 1985
Peterson, 1985, 86, 95
Bilotto, 1985
Keshner, 1992
Banovetz, 1995
Cordo and Nashner, 1982
Earl and Frank, 1992
Nouillot et al., 1992
Teasdale et al. 1993
Weeks et al., 1995
Stelmach et al., 1990

Gotlieb et al., Journal of Neurophysiology, vols 75 and 76 in 1996

Rosebaum, Human Motor Control, 1991

Talbott & Humphreys (eds) (1979) Posture and Movement, New York: Raven Press

Levin, Steve
Fuller's text Synergetics

Aurin & Latash (1995) Unified movement-posture control, Experimental Brain
Research, 106, 291-300.

??author- topic Lambda model: Brain and Behavior Science, 18, #14, 1995.