ELECTROMYOGRAPHIC ACTIVITY OF THE CERVICAL MUSCULATURE DURING DYNAMICLATERAL BENDING

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.