Scalene and sternomastoid muscle function

stewomastoid muscle functiotz. J. Appl. Physiol. 2 I (2) : 497-502. rc$%.----The present study tests and proves the hypothesis that scalcne muscles contract with increasing strength during up-\vard shift in respiratory position and delineates factors related to onset of accessory muscle activity. The scalene electromyo-gram obtained through needle electrodes was electrically rectified and integrated to quantify isometric muscle strength expressed as percentage of maximum. Sternomastoid electro-myogram, scalene electromyogram, and integral, intraesopha-geal pressure, mouth pressure, lung volume (bag-in-box sys-tem with wedge spirometer), and airflow (pneumotachograph) were recorded simultaneously. In all subjects scalene strength progressively increased as actively maintained, but stationary respiratory position approached full vital capacity. Compari-son of scalene strength with intraesophageal pressure durin