title: Assessing postural stability via the correlation patterns of vertical ground reaction force components.
abstract: BACKGROUND
  Many methods have been proposed to assess the stability of human postural balance by using a force plate. While most of these approaches characterize postural stability by extracting features from the trajectory of the center of pressure (COP), this work develops stability measures derived from components of the ground reaction force (GRF).
  
  
  METHODS
  In comparison with previous GRF-based approaches that extract stability features from the GRF resultant force, this study proposes three feature sets derived from the correlation patterns among the vertical GRF (VGRF) components. The first and second feature sets quantitatively assess the strength and changing speed of the correlation patterns, respectively. The third feature set is used to quantify the stabilizing effect of the GRF coordination patterns on the COP.
  
  
  RESULTS
  In addition to experimentally demonstrating the reliability of the proposed features, the efficacy of the proposed features has also been tested by using them to classify two age groups (18-24 and 65-73 years) in quiet standing. The experimental results show that the proposed features are considerably more sensitive to aging than one of the most effective conventional COP features and two recently proposed COM features.
  
  
  CONCLUSIONS
  By extracting information from the correlation patterns of the VGRF components, this study proposes three sets of features to assess human postural stability during quiet standing. As demonstrated by the experimental results, the proposed features are not only robust to inter-trial variability but also more accurate than the tested COP and COM features in classifying the older and younger age groups. An additional advantage of the proposed approach is that it reduces the force sensing requirement from 3D to 1D, substantially reducing the cost of the force plate measurement system.
authors.affiliation: Department of Mechanical and Electromechanical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan.
authors.forename: Chih-Yuan
authors.initials: CY
authors.lastname: Hong
authors.affiliation: Department of Sports Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Lan-Yuen
authors.initials: LY
authors.lastname: Guo
authors.affiliation: School of Engineering, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Song
authors.affiliation: Department of Mechanical Engineering, Marquette University, Milwaukee, WI, USA.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Nagurka
authors.affiliation: Department of Mechanical and Electromechanical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan.
authors.forename: Jia-Li
authors.initials: JL
authors.lastname: Sung
authors.affiliation: Department of Mechanical and Electromechanical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan. cmurobot@gmail.com.|Department of Physical Therapy, Kaohsiung Medical University, Kaohsiung, Taiwan. cmurobot@gmail.com.
authors.forename: Chen-Wen
authors.identifier: http://orcid.org/0000-0002-4894-7055
authors.initials: CW
authors.lastname: Yen
mesh_terms: D000058:Accidental Falls; D000293:Adolescent; D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D008875:Middle Aged; D004856:Postural Balance; D011312:Pressure; D012306:Risk; D055815:Young Adult
keywords: Force plate; Ground reaction force; Postural balance; Quiet standing