Instantaneous postural stability characterization using time-frequency analysis

Postural stability assessment is critical to a more accurate understanding of sway and balance control. The center of pressure (COP) metric has been shown to be a suitable output measure for time and frequency analysis. However, the center of pressure is a non-stationary signal. Standard time and fr...

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Bibliographic Details
Published in:Gait & posture 1999-10, Vol.10 (2), p.129-134
Main Authors: Ferdjallah, Mohammed, Harris, Gerald F., Wertsch, Jacqueline J.
Format: Article
Language:English
Subjects:
Adult
Balance
Center of pressure (COP)
Female
Humans
Instantaneous average power (IAP)
Instantaneous mean frequency (IMF)
Instantaneous spectral bandwidth (ISP)
Male
Muscle, Skeletal - physiology
Postural Balance - physiology
Postural control
Posture - physiology
Space life sciences
Time-frequency analysis
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Summary:Postural stability assessment is critical to a more accurate understanding of sway and balance control. The center of pressure (COP) metric has been shown to be a suitable output measure for time and frequency analysis. However, the center of pressure is a non-stationary signal. Standard time and frequency analysis methods may not be adequate for monitoring the dynamic changes in the center of pressure signal. In this study a time-frequency method, based on data-adaptive evolutionary spectral estimation, is applied to monitor the dynamic changes of the center of pressure in a non-stationary environment. Metrics including the instantaneous mean frequency (IMF), instantaneous spectral bandwidth (ISB), and instantaneous average power (IAP) are analyzed to characterize the center of pressure signal in both the anterior-posterior (AP) and the medial-lateral (ML) planes. Within the confines of this study, the IMF was found to be inversely proportional to IAP. The inverse proportionality factors were calculated in both eyes-open and eyes-closed trials during upright quiet standing. These findings suggest that the time-frequency analysis provides instantaneous metrics which describe the amplitude changes and frequency shift of the center of pressure under a variety of environmental conditions, thus providing a more reliable quantification of postural control.
ISSN:0966-6362
1879-2219
DOI:10.1016/S0966-6362(99)00023-5