Electromyographic study of the sternocleidomastoid muscle in head movements.

The function of the sternocleidomastoid muscle in head movements of 30 young individuals (19-28 years old, both sexes) was studied electromyographically using a TECA TE-4 electromyograph and Beckman surface electrodes. Action potentials were found in the following head movements: free heterolateral rotation; free homolateral inclination; free and counter-resistance protraction; free and counter-resistance flexion and free extension. These movements were performed with the subjects seated and in supine position.