The integrated roles of longus colli and sternocleidomastoid muscles: an electromyographic study.

Abstract

AbstractUsing bipolar fine‐wire electrodes, we examined the right and left longus colli (LC) and sternocleidomastoideus (StM) muscles electromyographically in ten healthy young adults. Action potentials were recorded on FM magnetic tape and each experiment was also videotaped. The head‐neck motions were recorded using a special neck goniometer. The muscles were studied in sitting, supine, prone and lateral positions, both during free movements and against resistance. There was complete inactivity in both muscles in relaxed sitting, normal breathing, deep expiration, and wet and dry swallowing. There was very marked synchronous EMG activity of the LC and StM muscles during resisted forward flexion, marked activity during neck flexion against head weight in the supine position, and during resisted right and left side‐bending. Variable activity was found in both muscles during deep breathing, coughing, forceful blowing, loading on top of the head, resisted backward extension, neck holding against head weight in the prone position and in twisting movements downwards and upwards. During free flexion‐extension movements, LC and StM act synchronously. During free lateral bending they work homolaterally, but during free rotation to the right, the right LC works with the left StM and vice versa.