Article

Quiet standing posture in humans has often been modeled as a single inverted
pendulum pivoting around the ankle joint. However, recent studies have suggested
that anti-phase action between leg and trunk segments plays a significant role in
stabilizing posture by reducing the acceleration of the center of mass (COM) of
the body. The aim of this study is to test the hypothesis that anti-phase action
is attenuated in the elderly compared to the young. The anterior-posterior
movements of leg and trunk segments were measured using 4 laser displacement
sensors from 22 healthy young subjects (age range, 20-35 years) and 38 healthy
elderly subjects (age range, 57-80 years) standing quietly for 30s twice. To
focus on the segmental action between trunk and legs, we applied constraints
(i.e., wooden splints) on each segment. We found that the velocity and
acceleration of the COM (standard deviation of the time series was evaluated)
were significantly higher for the elderly subjects than for young subjects. The
increase in the acceleration of the COM resulted not only from an increase in the
angular acceleration of the segments but also from the reduction of their
anti-phase relationship, as demonstrated by an index that quantifies the degree
of cancelation between both segments. We conclude that the degree of anti-phase
action between trunk and leg segments during quiet standing is smaller for
elderly subjects than for young subjects, and that this change of the anti-phase
action due to aging resulted in increased COM acceleration in the elderly
subjects.
CI - Copyright (c) 2014 Elsevier B.V. All rights reserved.

Langue : ANGLAIS