Participation of the sternocleidomastoid muscle on deep inspiration in man. An electromyographic study.

The sternocleidomastoid muscle (SCM), which is responsible for the mechanical action in the majority of the head movements, is also considered an accessory muscle for respiration. Its action in the inspiratory movements was studied electromyographically in 30 healthy young adults by considering the types of respiration, the different forms of deep inspiration, the breathing effort and the body position of these subjects. A prominent activity was found in those subjects whose respiration was of the costal type when they breathed rapidly and roughly and during the breathing effort. An outstanding difference of the action potentials of the SCM muscle was not observed during variation of the body positions.