Linked Life Data

19910338

Source:http://linkedlifedata.com/resource/pubmed/id/19910338

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2010-1-7
pubmed:abstractText
A matrix of 120 electromyogram (EMG) electrodes (8 rows and 15 columns) was used to investigate individual activation patterns of the medial (MG) and lateral gastrocnemius (LG) muscles during forward sways of the body in human quiet stance. This matrix was positioned on the right calf of eight subjects after identification of the MG and LG contours with ultrasound scanning. Gray-scale images were generated with the maxima and minima of the cross-correlation function between the envelope of each EMG signal and the body center of pressure (CoP) for individual forward sways. These images were automatically segmented to reduce the data set into representative and local values of EMG-CoP cross-correlation for each muscle. On average, modulations in EMG amplitude preceded the onset of forward sways with a variable timing, with both gastrocnemius muscles being similarly and synchronously modulated in 193 out of 236 sways. Variations in the timing of activation between muscles were less frequent, although consistent across subjects and significantly correlated with changes in the direction and velocity of body sways. Interestingly, the time shift between EMG and CoP traces sometimes varied consistently along different channels of the same column of electrodes, either in proximal-to-distal or distal-to-proximal direction. The variable EMG-CoP cross-correlation delay was not congruent with the delay expected for the propagation of surface potentials along muscle fibers. Comparison of surface EMGs with intramuscular EMGs recorded from six subjects demonstrated that surface potentials provide high spatial selectivity, thus supporting the notion of selective activation of motor units during quiet standing. Hence, the stabilization of the quiet standing posture likely relies on flexible rather than stereotyped mechanisms of control.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
1522-1601
pubmed:author
pubmed:issnType
Electronic
pubmed:volume
108
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
85-97
pubmed:meshHeading
pubmed:year
2010
pubmed:articleTitle
Is the stabilization of quiet upright stance in humans driven by synchronized modulations of the activity of medial and lateral gastrocnemius muscles?
pubmed:affiliation
Laboratory for Engineering of the Neuromuscular System, Politecnico di Torino, Via Cavali 22/H-10138, Torino, Italy.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't