Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 54, Issue 7 M343-M347, Copyright © 1999 by The Gerontological Society of America
Reliability of foot trajectory measures within and between testing sessions
GM Karst, PA Hageman, TF Jones and SH Bunner
Division of Physical Therapy Education, College of Medicine, University of Nebraska Medical Center, Omaha 68198-4420, USA. [email protected]
BACKGROUND: Impaired control of foot trajectory during the swing phase of
gait is hypothesized to increase the risk of slipping or tripping. Before
assessing the predictive validity of foot trajectory measures with respect
to incidence of falls, it is necessary to establish their reliability. The
purpose of this study is to assess within- and between- session reliability
of foot trajectory measures and traditional temporal-distance measures in
healthy elderly women during gait. METHODS: Sixteen healthy, elderly women
(ages 65-79 years) completed six sets of five trials each of natural and
fast cadence gait during a 3.5-hour period on each of 4 days. An
optoelectric motion analysis system and heel switches were used to obtain
both foot trajectory (minimum toe clearance during swing, vertical, and
horizontal heel contact velocities) and temporal-distance measures (step
width, cadence, velocity, stride length, and time). RESULTS: Within-session
test-retest reliability of all variables at natural and fast speeds was
good to excellent, with intraclass correlation coefficients (ICCs) of
greater than 0.9 for all but one measure (fast cadence stride time). ICCs
for between-session test-retest reliability were slightly lower, but still
greater than 0.9 for all but two measures (fast cadence stride time and
natural cadence vertical heel contact velocity). Heel contact velocities
quantified at the instant of heel contact correlated strongly with values
obtained by averaging over the last 2% of the gait cycle. DISCUSSION: The
good to excellent within- and between-session reliability of these foot
trajectory measures supports their use as a possible means of assessing
subtle changes in gait motor control. Confirmation of an association
between alterations in foot trajectory measures and incidence of falls
awaits further study.
