Objective—To assess the reliability of the center-ofpressure
(COP) values obtained from a force platform
for analysis of postural sway in horses.
Animals—Six 2-year-old horses that were free from
lameness and neurologic disease.
Procedure—Horses stood stationary with all 4
hooves on a force platform; COP data were collected
at 1,000 Hz and 3-dimensional kinematics collected at
60 Hz for 10 seconds. Five trials were recorded at
each of 3 time periods (15-minute intervals) or at 1
time period on 3 separate days. Mean values for each
set of 5 trials and actual, normalized, and relative COP
variables were calculated. The reliability was quantified
by use of agreement boundary.
Results—The COP results within and across days
were similar and provided small agreement boundary
limits (eg, across days, in order of least relative reliability:
area, ± 62 mm2; mediolateral range, ± 8 mm;
radius, ± 2 mm; craniocaudal range, ± 4 mm; and
velocity, ± 3 mm/s). Head height possessed the greatest
relative intraday reliability (12%) but a high agreement
boundary limit (± 0.15 m).
Conclusions and Clinical Relevance—The use of a
force platform to analyze postural sway in a group of
young healthy horses was found to produce reliable
results and may provide a simple and sensitive measure
for assessing balance deficiencies in horses.
Agreement boundaries provide 95% confidence intervals
for use as limits of error and variability in measurements
that, if exceeded, may signify meaningful
effects. (Am J Vet Res 2003;64:1354–1359)