Medical Journal of The Islamic Republic of Iran (MJIRI)

  Abstract

  Background: Postural instability has been identified as a potential precursor of

  falls in elderly subjects. Postural stability in quiet stance is commonly assessed with

  center of pressure (COP) measures. The purpose of this study was to determine testretest reliability and minimal detectable change (MDC) for the center of pressure

  (COP) measures in the elderly subjects.

  Methods: Eighteen healthy elderly people over the age of 60 years participated in

  this study. For each subject the COP was recorded during quiet upright stance on different levels of postural difficulty (eyes open versus eyes closed, firm surface versus

  foam surface) and lean condition (forward and backward). All measurements were

  done on two sessions with 7 days interval. These indices: mean velocity, standard deviation of amplitude, standard deviation of velocity, phase plane parameter and area

  (95% confidence ellipse). Intraclass correlation coefficient (ICC), standard error of

  measurement (SEM) and coefficient of variation (CV) were used to quantify testretest

  reliability. The MDC for each measure was calculated to quantify intervention

  effects.

  Results: In general, test-retest reliability of COP measures in the elder subjects

  was increased whenever postural difficulty of task increased in quiet standing. In

  standing conditions, mean velocity and phase plane parameter were the most sensitive

  and the most reliable measures. The lean range was the most sensitive and the

  most reliable measure, in the lean conditions.

  Conclusion: Center of pressure measures in the quiet standing especially in difficult

  postural conditions demonstrated high sensitivity in the older subjects. These results

  may be useful in quantification and assessment of balance performance and

  treatment efficacy.