Article

External perturbation of the trunk via sudden loading and unloading is an
established method to study control of spinal stability and postural equilibrium.
As differential control of the deep and superficial lumbar multifidus occurs
during predictable sagittal loading, we hypothesized that the deep and
superficial components of the thoracic paraspinal muscles would also be
differentially active during loading and unloading of the trunk. Variation in
sagittal mobility between regions of the thorax and previous data of differences
in control of the thoracic paraspinal muscles between regions in other tasks
supported a hypothesis that there would be region-specific differences in
responses to loading and unloading. This study used fine-wire electrodes to
record electromyographic (EMG) activity from the right deep
(multifidus/rotatores) and superficial (longissimus) muscles at T5, T8, and T11
in ten healthy subjects during predictable and unpredictable sudden loading and
unloading of the trunk. EMG amplitude was calculated during 10 ms epochs for 50
ms before the onset of trunk perturbation and 150 ms after the perturbation.
Contrary to our hypotheses, deep and superficial thoracic paraspinal muscles were
similarly active (loading: p=0.470; unloading: p=0.137) and similarly affected by
the degree of predictability at all levels. Thus, deep and superficial thoracic
paraspinal muscles are recruited en bloc during sagittal plane trunk
perturbations. This contrasts previous findings of differential control between
the deep and superficial thoracic paraspinal muscles during rotational tasks, and
provides evidence that discrete control of thoracic paraspinal muscle fascicles
is specific to the direction of forces applied to the trunk.
CI - Copyright (c) 2011 Elsevier B.V. All rights reserved.
Electromyographie

Langue : ANGLAIS