Ww. Lu et Pj. Bishop, ELECTROMYOGRAPHIC ACTIVITY OF THE CERVICAL MUSCULATURE DURING DYNAMICLATERAL BENDING, Spine (Philadelphia, Pa. 1976), 21(21), 1996, pp. 2443-2449
Study Design. Electromyographic profiles from the neck muscles of five
young, healthy men were obtained to study the muscular activation pat
terns during dynamic external loading. Objectives. To examine the myoe
lectric activity of selected cervical muscles during dynamic loading,
and to explore the reaction of the cervical muscles to different loadi
ng conditions. Summary of Background Data. The response of cervical mu
scles throughout dynamic external loading is not well understood. Elec
tromyography provides information, within certain limitations, about t
he neural drive to various components of the musculature. Such informa
tion on activation, combined with geometric parameters of the musculos
keletal tissues, constitutes a tool for helping to understand the mech
anism of head and neck impact-related injury. Methods. Subjects were t
ested with the head and neck in the neutral and prebent positions. Dyn
amic loads were applied laterally to each subject by free-falling mass
es to create peak dynamic loads ranging from about 40 to 100 N. Force
and electromyographic data were recorded, and cross-correlations from
linear envelope electromyography were calculated. Results. The peak el
ectromyogram showed large differences between the two applied loads an
d between subjects. There were time delays (75-165 msec) between the p
eak applied force and the peak electromyogram. The muscles on the cont
ralateral side demonstrated different electromyographic profiles betwe
en subjects. Within subjects, the electromyographic profiles from each
muscle were consistent for the same trial conditions. Conclusions. El
ectromyographic profiles and the cross-correlation coefficients for ce
rvical muscles have shown reproducible intrasubject muscle synergies,
which were not sensitive to the magnitude of applied load and the post
ure of the head, Intersubject muscle activity patterns varied.