Bl. Davis et Cl. Vaughan, PHASIC BEHAVIOR OF EMG SIGNALS DURING GAIT - USE OF MULTIVARIATE-STATISTICS, Journal of electromyography and kinesiology, 3(1), 1993, pp. 51-60
The present study represents an attempt to ascertain whether there are
some underlying trends that, in some combination, can explain all the
variations in the linear envelopes of 16 EMG signals of selected leg
muscles. Two kinds of analyses were performed: (a) a factor analysis o
f EMG data corresponding to 16 muscles of the lower limb and (b) a ''m
ulti-dimensional scaling'' (MDS) procedure. The latter technique invol
ved mapping the Cartesian coordinates for 16 points subject to the con
straint that the distance between any two points reflected the degree
of coactivity for the corresponding muscles. The results of these anal
yses showed that four factors could account for 91.5% of the variance
in the original data set. These factors could be clearly demarcated on
the ''muscle map,'' tending to support the notion that there are moto
r ''programs'' for groups of muscles that have to perform a given func
tion during locomotion. Further analysis of the loading matrix (i.e.,
correlations between each EMG vector and each of the four factors) sho
wed groups of muscles that acted in a similar manner. The muscle group
s could be divided into those that act at the times of (a) heelstrike,
(b) single limb loading response, (c) propulsion phase, or else (d) a
cted in a biphasic manner.