Sequential activation of axial muscles during different forms of rhythmic behavior in man.
Exp Brain Res. 2007-10-17; 185(2): 237-247
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1. Exp Brain Res. 2008 Feb;185(2):237-47. Epub 2007 Oct 17.
Sequential activation of axial muscles during different forms of rhythmic
behavior in man.
de Sèze M(1), Falgairolle M, Viel S, Assaiante C, Cazalets JR.
(1)Université Bordeaux 2, CNRS UMR 5227, Zone nord Bat 2, 2e étage, 146, rue Léo
Saignat, 33076 Bordeaux Cedex, France.
In humans, studies of back muscle activity have mainly addressed the functioning
of lumbar muscles during postural adjustments or rhythmic activity, including
locomotor tasks. The present study investigated how back muscles are activated
along the spine during rhythmical activities in order to gain insights into
spinal neuronal organization. Electromyographic recordings of back muscles were
performed at various trunk levels, and changes occurring in burst amplitudes and
phase relationships were analyzed. Subjects performed several rhythmic behaviors:
forward walking (FW), backward walking (BW), amble walking (where the subjects
moved their arms in phase with the ipsilateral leg), walking on hands and knees
(HK) and walking on hands with the knees on the edge of a treadmill (Hand). In a
final task, the subjects were standing and were asked to swing (Swing) only their
arms as if they were walking. It was found that axial trunk muscles are
sequentially activated by a motor command running along the spinal cord (which we
term « motor waves ») during various types of locomotion or other rhythmic motor
tasks. The bursting pattern recorded under these conditions can be classified
into three categories: (1) double-burst rhythmic activity in a descending (i.e.,
with a rostro-caudal propagation) motor wave during FW, BW and HK conditions; (2)
double-burst rhythmic activity with a stationary motor wave (i.e., occurring in a
single phase along the trunk) during the ‘amble’ walk condition; (3) monophasic
rhythmic activity with an ascending (i.e., with a caudo-rostral propagation)
motor wave during the Swing and Hands conditions. Our results suggest that the
networks responsible for the axial propagation of motor activity during
locomotion may correspond to those observed in invertebrates or lower
vertebrates, and thus may have been partly phylogenetically conserved. Such an
organization could support the dynamic control of posture by ensuring fluent
movement during locomotion.
PMID: 17940760 [Indexed for MEDLINE]