title: In-shoe center of pressure: indirect force plate vs. direct insole measurement.
abstract: BACKGROUND
  In-shoe center of pressure (COP) measurement is essential in biomechanics. COP can be measured directly utilizing pressure-sensitive insoles, or calculated indirectly via force plate-generated data. While the latter does not require the use of additional measurement hardware (shoe insoles), its precision at calculating in-shoe COP has not been determined. Our purpose was to ascertain the precision of force plate in-shoe COP calculations and enhance their accuracy through a mathematical algorithm.
  
  
  METHODS
  Twelve male students participated in the study. In-shoe COP was measured synchronously via the Pedar-X insole system and AMTI force plates, comparing the measurements of both systems. A mathematical algorithm was created to improve agreement between the systems and comparisons were recalculated.
  
  
  RESULTS
  The two methods showed different measurements of in-shoe COP. The medio-lateral (ML) and anterior-posterior (AP) Pearson correlation coefficients between systems were 0.44 ± 0.35 and 0.99 ± 0.01, and the ML and AP RMS errors were 6.3 ± 3.0 mm and 43.0 ± 12.5 mm, respectively. Using a mathematical algorithm, the differences between the measurements of each system could be reduced significantly (all P<0.001).
  
  
  CONCLUSIONS
  Without adjustment, force plates give an approximate location of the COP. Using an adjustment model greatly improves the accuracy of the COP trajectory during stance.
authors.affiliation: Biorobotics and Biomechanics Lab, Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa, Israel. eytan.debbi@aya.yale.edu
authors.forename: Eytan M
authors.initials: EM
authors.lastname: Debbi
authors.forename: Alon
authors.initials: A
authors.lastname: Wolf
authors.forename: Yulia
authors.initials: Y
authors.lastname: Goryachev
authors.forename: Ziva
authors.initials: Z
authors.lastname: Yizhar
authors.forename: Elhanan
authors.initials: E
authors.lastname: Luger
authors.forename: Ronen
authors.initials: R
authors.lastname: Debi
authors.forename: Amir
authors.initials: A
authors.lastname: Haim
mesh_terms: D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D011312:Pressure; D012775:Shoes; D055815:Young Adult