Article

The ankle extensors play a dominant role in controlling the equilibrium during
bipedal quiet standing. Their primary role is to resist the gravity toppling
torque that pulls the body forward. The purpose of this study was to investigate
whether the continuous muscle activity of the anti-gravity muscles during
standing is triggered by the joint torque requirement for opposing the gravity
toppling torque, rather than by the vertical load on the lower limbs. Healthy
adults subjects stood on a force plate. The ankle torque, ankle angle, and
electromyograms from the right lower leg muscles were measured. A ground-fixed
support device was used to support the subject at his/her knees, without changing
the posture from the free standing one. During the supported condition, which
eliminates the ankle torque requirement while maintaining both the vertical load
on the lower limbs and the natural upright standing posture, the plantarflexor
activity was attenuated to the resting level. Also, this attenuated plantarflexor
activity was found only in one side when the ipsilateral leg was supported. Our
results suggest that the vertical load on the lower limb is not determinant for
inducing the continuous muscle activity in the anti-gravity muscles, but that it
depends on the required joint torque to oppose the gravity toppling torque.
CI - Copyright (c) 2012 Elsevier B.V. All rights reserved.

Langue : ANGLAIS