Article

Postural balance assessments are performed in both clinical and basic
research settings on a daily basis. During a 24-h time span our physiology and
physical performance undergo radical changes as we are influenced by the
circadian rhythm. The time-of-day interaction on postural balance is unknown in
older adults. The aim of this study was to investigate the time-of-day effect on
postural balance in older adults. METHODS: Center of pressure (CoP) excursion was
measured (100 Hz) by force plate analysis in 34 older adults during 30 s of
narrow quiet bilateral stance. Measurements were performed around 9a.m., 12.30
p.m. and 4 p.m. on the same day. Postural balance was quantified by
velocity-moment, confidence ellipse area, total sway area and total sway length.
RESULTS: An overall significant time-of-day (between 9 a.m. and 4 p.m.) effect
was observed for velocity-moment (mm(2)/s) 57 +/- 27-65 +/- 29 (p = 0.001),
confidence ellipse area (mm(2)) 36 +/- 16-44 +/- 19 (p < 0.001), total sway area
(mm(2)) 548 +/- 263-627 +/- 285 (p = 0.001) and total sway length (mm) 373 +/-
120-379 +/- 113 (p = 0.037). The variation of postural balance was mostly
pronounced from midday (12.30 p.m.) toward the afternoon (4 p.m.) in all sway
parameters. Specifically between 12.30 p.m. and 4 p.m. confidence ellipse area
increased by 18.5%, total sway area by 17.1%, velocity-moment by 15.8% and total
sway length by 4.6%. No differences were observed between 9 a.m. and 12.30 p.m.
in any of the sway parameters. CONCLUSIONS: This study demonstrates that
time-of-day influences postural balance in older adults. These findings have
important scientific and clinical relevance, as they imply that time-of-day
should be a controlled factor when assessing postural balance in older adults.
CI - Copyright (c) 2011 Elsevier B.V. All rights reserved.

Langue : ANGLAIS