Research Article
Early Postural Instability in Parkinson’s Disease: A Biomechanical Analysis of the Pull Test
Table 1
Posturographic variables.
| Posturographic variables | Definition |
| General statistics (cm): | | X avg | Average displacement of the CoP in the lateral (X) axis of the platform | X right | Maximum displacement of the CoP in the right direction | X left | Maximum displacement of the CoP in the left direction | X SD | Standard deviation of the mean displacement of the CoP in the lateral (X) axis | Y avg | Average displacement of the CoP in the anterior-posterior (Y) axis of the platform | Y ant | Maximum displacement of the CoP in the anterior direction | Y post | Maximum displacement of the CoP in the posterior direction | Y SD | Standard deviation of the mean displacement of the CoP in the anterior-posterior (Y) axis |
| Velocity measures (cm/s) | | Vx right | Maximum velocity of the CoP in the right direction | Vx left | Maximum velocity of the CoP in the left direction | Vy ant | Maximum velocity of the CoP in the anterior direction | Vy post | Maximum velocity of the CoP in the posterior direction | V avg | Average velocity of the CoP |
| Sway areas (cm2) | | Rectangular area | Rectangular area that encompasses 100% of the data | Circular area | Circular area that encompasses 100% of the data | Area95 | 95th percentile of an ellipse fitted to the overall CoP trace | Major95 (cm) | Length of the major axis of the 95th percentile ellipse | Minor95 (cm) | Length of the minor axis of the 95th percentile ellipse | Path length (cm) | Total distance covered by the CoP |
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CoP: center of pressure; cm: centimeters; s: seconds.
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