Can the pliance pressure mat accurately locate the cop position in a standing subject
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Can the pliance pressure mat accurately locate the COP position in a standing subject?. Why?. Measurement of standing posture common in the assessment of: Neurological disorders (eg. Parkinsons) Affect of age Surgical intervention Strength and conditioning Exercise

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Can the pliance pressure mat accurately locate the cop position in a standing subject
Why? position in a standing subject?

  • Measurement of standing posture common in the assessment of:

    • Neurological disorders (eg. Parkinsons)

    • Affect of age

    • Surgical intervention

    • Strength and conditioning

    • Exercise

    • Sports that require stable base eg. Golf putting, shooting, archery, etc

  • Indicator of postural control


Can the pliance pressure mat accurately locate the cop position in a standing subject
Why? position in a standing subject?

  • Indicates body’s reaction to accelerations of the COM

    • “Ankle technique” to adjust posture

    • COP always within base of support

    • Indicates position of GRFs


Can the pliance pressure mat accurately locate the cop position in a standing subject
How? position in a standing subject?

  • Typically, research has been conducted by measuring the displacement of the COP using a force platform


What is calculated
What is calculated? position in a standing subject?

  • Range of COP movement in AP and ML directions

    • Max y co-ord

    • Min y co-ord

    • Max x co-ord

    • Min x co-ord

    • Total displacement

    • Over total time and at discrete points (1sec, 5sec,etc.)

  • Area

  • COP average velocity


Disadvantages of force plates
Disadvantages of force plates position in a standing subject?

  • Portability?

    • Access to subjects limited

  • No discrimination of feet

    • COP of whole body only

    • No information on COP location in feet

    • Unknown distance between feet

    • Proportional L/R weighting unknown

    • (AccuSway requires user to locate feet)


Cop measurement using pliance
COP measurement using pliance position in a standing subject?

  • All parameters provided by force plate can be calculated post measurement

    • Range data

    • Area

    • Velocity

    • Total displacement


Comparison of pliance to amti
Comparison of pliance to AMTI position in a standing subject?

  • Method

    • AMTI strain gauge plate, 500Hz,

    • Pliance mat 392 (16x16, 6cm2), 38.5Hz, 8.2 software

    • Data collection synchronised through Amlab software

    • 1st picture sync pulse from pliance

    • Many trials, different subjects, different tasks

    • Eliminated trials because of edge data and saturation


Copx v copy scatter plot examples
COPx v COPy scatter plot examples position in a standing subject?

AMTI data Pliance data


Copx v copy scatter plot examples1
COPx v COPy scatter plot examples position in a standing subject?

AMTI data Pliance data


Copx v copy scatter plot examples2
COPx v COPy scatter plot examples position in a standing subject?

AMTI data Pliance data


Can the pliance pressure mat accurately locate the cop position in a standing subject

Combined range data for all trials position in a standing subject?

Combined Error data for all trials

COPy pliance (mm)

COPy abs (mm)

COPy AMLAB (mm)

COPy rel

(% )

COPx abs (mm)

COPx pliance (mm)

COPx AMLAB (mm)

COPx rel

(%)

Mean

0.27

1.67

0.11

0.37

Mean

19.71

19.44

11.88

11.78

Stdev

0.75

4.07

0.44

4.62

Stdev

21.68

21.28

5.35

5.2

Accuracy of pliance COP range data (using AMTI as gold standard – error calculated as difference from AMTI output)


Accuracy of pliance cop range data

Statistical position in a standing subject?

parameters

(mm)

 (mm)

PD (mm)

d

F calc

p

COPy

19.57

21.29

0.979

0.172

0.122

0.002

0.033

COPx

11.83

5.23

0.59

0.423

0.297

0.006

0.053

Accuracy of pliance COP range data

  • Non-central F distribution to assess “equality”

  • Where d is effect size,  is the non-centrality parameter, PD is practical difference

  • This indicates that the COP range data from the pliance pressure system is of equal accuracy to the COP output of the AMTI force plate.


Implications for novel
Implications for novel position in a standing subject?

  • Ability of flexible mat to provide accurate COP information in standing subjects

    • Note also that resolution of system was not highest available

  • Many advantages of pliance “posturography” system over force plate systems


Advantages of pliance over force plate
Advantages of pliance over force plate position in a standing subject?

  • Highly portable

    • Go to subjects rather than subjects come to researcher eg. Could measure next to bed in hospital

  • Simple set up (flat surface)

  • Combination with recorder or player


Advantages of pliance over force plate1
Advantages of pliance over force plate position in a standing subject?

  • Most importantly analysis can easily provide information on each foot (if double support)

    • COP total range x,y, COP left/right, within foot

    • COP location as % of distance between feet

    • Individual feet loading information (force)

    • Interactions between feet


Future applications modifications
Future applications/modifications position in a standing subject?

  • Biofeedback

    • By increasing the size of the display in online mode and centreing display

    • OR bars to indicate left/right loading

    • AND bars to indicate back forward loading

    • OR numerical display to indicate position of COP left/right

    • Collect data with masks

    • Report protocol