Article

Transports publics -
Abstract : Maintaining balance while standing on a moving bus or subway is challenging, and
falls among passengers are a significant source of morbidity. Standing passengers
often rely on handrail grasping to resist perturbations to balance. We conducted
experiments that simulated vehicle starts, to examine how handrail location
(overhead or shoulder-height), perturbation direction (forward, backward, left or
right), and perturbation magnitude (1 or 2m/s(2)) affected the biomechanical
effort (peak centre-of-pressure (COP) excursion and hand force) and muscle
activations (onset and integrated EMG activity) involved in balance maintenance.
COP excursions, hand forces and muscle activations were altered in a functional
manner based on task constraints and perturbation characteristics. Handrail
position affected normalized values of peak COP and hand force during forward and
backward, but not sideways perturbations. During backward perturbations, COP
excursion was greater when grasping overhead than shoulder-height. During forward
perturbations, hand force was greater when grasping shoulder-height than
overhead. Biceps activations were earlier during shoulder-height than overhead
grasping, while tibialis anterior activity was higher during overhead than
shoulder-height grasping. Our results indicate that, when facing forward or
backward to the direction of vehicle motion, overhead grasping minimizes hand
force, while shoulder-height grasping minimizes COP excursion. In contrast,
grasping with a sideways stance eliminates the effect of handrail location, and
was associated with equal or lower biomechanical effort. This suggests that, at
least for vehicle starts, the most reasonable strategy may be to stand sideways
to the direction of the vehicle movement, and grasp either at shoulder-height or
overhead.
CI - Copyright (c) 2013 Elsevier B.V. All rights reserved.

Langue : ANGLAIS