SELECTIVE ELECTROMYOGRAPHY OF DORSAL NECK MUSCLES IN HUMANS

The patterns of activation of splenius capitis, semispinalis capitis, transversospinalis, and levator scapulae muscles were studied during v arious head-neck positions, movements, and isometric tests in 19 healt hy human subjects. Myoelectric activities were recorded with intramusc ular bipolar wire electrodes. Cervical computerized tomography of each subject was performed before the electromyography session in order to guide electrode insertion. Head motion was recorded using an electrom echanical device. This report demonstrates that head motion results fr om a complex interaction of active muscular forces, passive ligamentou s forces, and gravity. Splenius capitis has two main functions, i.e., cervical extension and ipsilateral rotation. Semi spinalis capitis and the transversospinalis are mainly extensors, and levator scapulae act s primarily on the shoulder girdle. Splenius capitis, semispinalis cap itis, and transversospinalis play a subordinate part in ipsilateral ti lting. In addition, most subjects' semispinalis capitis were gradually recruited during ipsilateral rotation. No signal was detected from th e transversospinalis during rotation tests.