R. Happee et Fct. Vanderhelm, THE CONTROL OF SHOULDER MUSCLES DURING GOAL-DIRECTED MOVEMENTS, AN INVERSE DYNAMIC ANALYSIS, Journal of biomechanics, 28(10), 1995, pp. 1179-1191
Fast goal directed arm movements in the sagittal plane were analyzed w
ith a three-dimensional shoulder model with 95 muscle elements, Dynami
cs of the muscle elements were described by a third-order nonlinear mu
scle model. Muscle forces and activation were estimated using the meth
od of inverse muscular dynamics, an optimization scheme which uses onl
y very limited computational power. Most model results were similar to
the EMG but some differences between model results and EMG were found
in muscles where the EMG activity was subject dependent. For the move
ment studied, the thoracoscapular muscles were shown to deliver about
40% of the energy required for the acceleration of the arm during ante
flexion and about 22% during retroflexion. Activity of thoracoscapular
muscles was also required to ensure contact between the thorax and th
e scapula which is important for the mechanical stability of the shoul
der. The rotator cuff muscles were found to deliver about 19% of the e
nergy required for the acceleration of the arm during anteflexion and
about 8% during retroflexion.