Action of abdominal muscles on rib cage in humans

Abstract

To assess the actions of the rectus abdominis and external oblique muscles on the rib cage in humans, these two muscles were stimulated with surface electrodes in four normal supine subjects at functional residual capacity. Changes in anteroposterior and transverse rib cage diameters and changes in xiphipubic distance were measured with pairs of magnetometers. Stimulation of rectus abdominis produced a marked decrease in the xiphipubic distance and in the anteroposterior diameter, thus making the rib cage more elliptic. In contrast, stimulation of the external oblique caused a decrease in the transverse diameter, making the rib cage more cylindrical. When both muscles were stimulated simultaneously, the resultant rib cage distortion depended on the relative voltage at which each muscle was stimulated. Electromyogram recordings showed that there was no cross contamination or activity of the diaphragm during the muscle stimulations. Transdiaphragmatic pressure increased with the voltage of stimulation, suggesting passive lengthening of the diaphragm. X-ray studies were performed in two subjects and confirmed the main magnetometer findings. These studies thus confirm that the rib cage in humans is more easily distortable than conventionally thought. The abdominal muscles can distort it in either direction depending on which muscles are contracting.

Effects of respiratory muscle training and electrical stimulation of abdominal muscles on respiratory capabilities in tetraplegic patients

“…It has been demonstrated that isolated stimulation of the rectus abdominis in healthy humans produces a marked caudal displacement of the sternum and a large decrease in the rib cage anteroposterior diameter. 18,19 Our results con®rm such action in tetraplegic patients. RT measurements were greater when the patient's voluntary e ort was combined with ES of abdominal muscles than when it was not.…”

The The abdominal muscles – a functional review

“…Indirectly these muscles by increasing intra abdominal pressure cause passive distension of the diaphragm which by acting over its zone of apposition to the lower rib cage expands this part of the rib cage (Mier et al, 1985). The RA and EO each act differently on the rib cage.…”

“…When activated together, the distortion of the rib cage will depend on the relative strength of contraction of each of the muscles. The IO and TA were not tested (Mier et al, 1985).…”

The Correlation Between Peak Expiratory Flow and Abdominal Muscle Thickness in Elderly Females

“…These include the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and transverse abdominis muscles (TrA). The action of the RA produces a caudal displacement of the sternum, and a decrease in the anteroposterior diameter of the rib cage (4). Contraction of the EO causes a caudal displacement and a decrease in the transverse diameter of the rib cage (4).…”

“…The action of the RA produces a caudal displacement of the sternum, and a decrease in the anteroposterior diameter of the rib cage (4). Contraction of the EO causes a caudal displacement and a decrease in the transverse diameter of the rib cage (4). The activities of the TrA and IO are related to changes in intraabdominal pressure (5).…”