Article

People with multiple sclerosis (MS) have diminished postural control,
and center of pressure (COP) displacement varies more in this population than in
healthy controls. Balance-based torso-weighting (BBTW) can improve clinical
balance and mobility in people with MS, and exploration using both linear and
nonlinear measures of COP may help determine whether BBTW optimizes movement
variability. The aim of this study was to investigate the effects of
BBTW on people with MS and healthy controls during quiet standing. DESIGN: This
was a quasi-experimental study comparing COP variability between groups, between
eye closure conditions, and between weighting conditions in the
anterior-posterior and medial-lateral directions. METHODS: Twenty participants
with MS and 18 healthy controls stood on a forceplate in 4 conditions: eyes open
and closed and with and without BBTW. Linear measures of COP displacement
included range and root mean square (RMS). Nonlinear measures included
approximate entropy (ApEn) and Lyapunov exponent (LyE). Three-way
repeated-measures analyses of variance compared measures across groups and
conditions. The association between weighting response and baseline nonlinear
variables was examined. When significant associations were found, MS subgroups
were created and compared. RESULTS: The MS and control groups had significantly
different range, RMS, and ApEn values. The eyes-open and eyes-closed conditions
had significantly different range and RMS values. Change with weighting
correlated with LyE (r=-.70) and ApEn (r=-.59). Two MS subgroups, with low and
high baseline LyE values, responded to BBTW in opposite directions, with a
significant main effect for weighting condition for the LyE variable in the
medial-lateral direction. LIMITATIONS: The small samples and no identification of
impairments related to LyE at baseline were limitations of the study.
CONCLUSIONS: The LyE may help differentiate subgroups who respond differently to
BBTW. In both subgroups, LyE values moved toward the average of healthy controls,
suggesting that BBTW may help optimize movement variability in people with MS.
CI - (c) 2014 American Physical Therapy Association.

Langue : ANGLAIS