How many strides are required for a reliable estimation of temporal gait parameters? Implementation of a new algorithm on the phase coordination index

Abstract

BackgroundThe Phase coordination index (PCI), a temporal gait measure that quantifies consistency and accuracy in generating the anti-phased left-right stepping pattern, assesses bilateral coordination of gait in various cohorts (e.g., Parkinson's disease, post stroke). As PCI is based on mean values calculated across a series of gait cycles, individuals are required to perform lengthy walking trials, prolonging gait assessments which cause discomfort to some of them. This study introduces an algorithm to identify the required number of strides to obtain a reliable, characteristic PCI value.MethodsSimulated data sets, as well as physiological data (obtained from healthy elderly and young persons, from over ground and treadmill trials) were used in this research. A series of N-1 PCI values was calculated for i = 2,3,4…N gait cycles for each participant. There is a value i = k, representing certain number of cycles, for which no significant change in PCI occurs as additional cycles are added, termed point of stabilization (POS). The algorithm presented here uses a 2-stage iterative process to determine POS. Stage 1 searches for the gross location of the interval of PCI values containing the POS. In stage 2, the algorithm performs a high-resolution recursive, iterative process within this interval to find the exact point. The criterion for defining stability within a window of PCI values is a coefficient of variation (CV) of ≤ 5%.ResultsOur recursive, iterative algorithm indicates that ~23 strides on average should be captured to attain a characteristic PCI.ConclusionsGait trials with at least 23 strides on average should suffice to obtain a reliable estimation of PCI in healthy young adults. While this methodology may be considered generic, future studies should obtain POS values based on additional cohorts (e.g., disabled participants, fixed walking speeds).

Associations between gait coordination, variability and motor cortex inhibition in young and older adults

“…Interlimb bilateral coordination was determined using PCI. Phase coordination index measures the degree of consistency and accuracy in generating a series of anti-phase left-right stepping phases (Kribus-Shmiel et al;. The PCI calculation has been described previously (M. Plotnik et al, 2007).…”

“…Although traditional spatiotemporal metrics of gait are useful in assessing mobility, coordination and variability measures appear to distinguish gait limitations with more specificity (Brach et al, 2001;Brach et al, 2007;Dingwell, Salinas, & Cusumano, 2017;James et al, 2016;Kang & Dingwell). Gait coordination is the ability to appropriately time left-right stepping patters within the construct of a stride during walking, commonly quantified using the phase coordination index (PCI) (James, Leveille, Hausdorff, Barton, et al, 2017;Kribus-Shmiel, Zeilig, Sokolovski, & Plotnik, 2018;. Gait variability is typically defined as the kinetic stride-to-stride fluctuations of multiple gait cycles over a period of time and distance (Lord, Howe, Greenland, Simpson, & Rochester, 2011).…”

Reliability of a multi‐segment foot model in a neutral cushioning shoe during treadmill walking

“…The majority of test-retest reliability studies use 3–10 cycles per session, with one particular study choosing only 3 strides after visually identifying the best of all traces of the session, which presents some bias [ 16 ]. A recent study found that approximately 23 strides on average should be captured to attain a reliable characteristic phase coordination index in healthy young adults [ 21 ]. The phase coordination index is a temporal measure that assesses bilateral coordination of gait.…”

Gait Analysis in a Box: A System Based on Magnetometer-Free IMUs or Clusters of Optical Markers with Automatic Event Detection

“…The 25 straight strides measured in each test were chosen according to Kribus-Shmiel et al [22], who assured that statistical stability and normality were achieved within 23 strides, and that this number of strides was sufficient to represent the mean behaviour in gait analysis.…”