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. Author manuscript; available in PMC: 2016 May 12.
Published in final edited form as: Pediatr Phys Ther. 2015 Winter;27(4):316–327. doi: 10.1097/PEP.0000000000000193

TABLE 1.

A Summary of the Center-of-Pressure (COP) Trajectory Metrics Used in This Study

Metric Type Basic Description
Path length (PL) Vamount Distance COP traveled during a given trial (Figure 3A)
Center-of-pressure area (COP area) Vamount Area of an ellipse fitted to 95% of the data (Figure 3B)
Standard deviation (SD) Vamount The dispersion of positions of the COP around the mean position of the COP in either the anterior-posterior or medial-lateral time series (the lighter lines in Figure 4A and B)
Sample entropy (SampEn) Vstructure Probability that a small segment of the COP trajectory will be reproduced at a later time in the time series (Figure 5)
Renyi entropy (RenyiEn) Vstructure Probability that a measured COP position will reside in a given location (Figure 6)

Abbreviations: Vamount, amount of variability; Vstructure, structure of the variability.