Article

Modulation of lower limb somatosensory information by tendon or plantar vibration
produces directionally specific, vibration-induced falling reactions that depend
on the tendon or the region of the sole that is vibrated.
This study
characterized the effects of different patterns of plantar cutaneo-muscular
vibration and bilateral Achilles tendon vibration (ATV) on the postural
strategies observed during quiet and perturbed stance. Twelve healthy young
participants stood barefooted, with their vision blocked, on two sets of plantar
vibrators placed on two AMTI force plates embedded in a moveable support surface.
Two other vibrators were positioned over the Achilles tendons. Participants were
randomly exposed to different patterns of plantar cutaneo-muscular and ATV. Tilts
of the support surface in the toes-up (TU) and toes-down (TD) directions were
given 5-8s after the beginning of vibration. Body kinematics in 3D and ground
reaction forces were recorded. Bilateral ATV applied with or without rearfoot
vibration (RFV) during quiet stance resulted in a whole-body backward leaning
accompanied by an increase in trunk extension and hip and knee flexion. RFV alone
produced a forward whole-body tilt with increased flexion in trunk, hip, and
ankle. When stance was perturbed by TU tilts, the center of mass (CoM) and center
of pressure (CoP) displacements were larger in the presence of RFV or ATV and
associated with increased peak trunk flexion. TD tilts with or without ATV
resulted in no significant difference in CoM and CoP displacements, while larger
trunk extension and smaller distal angular displacements were observed during
ATV. RFV altered the magnitude of the balance reactions, as observed by an
increase in CoP displacements and variable response in trunk displacement.
Significant interactions between ATV and RFV were obtained for the peak angular
excursions for both directions of perturbations, where ATV either enhanced (for
TU tilts) or attenuated (for TD tilts) the influence of RFV. Manipulating
somatosensory information from the plantar cutaneo-muscular and muscle spindle Ia
afferents thus results in altered and widespread postural responses, as shown by
profound changes in body kinematics and CoM and CoP displacements. This suggests
that the CNS uses plantar cutaneo-muscular and ankle spindle afferent inputs to
build an appropriate reference of verticality that influences the control of equilibrium during quiet and perturbed stance.
CI - Copyright (c) 2010 Elsevier B.V. All rights reserved.

Langue : ANGLAIS