Electromyography activity of the rectus abdominis, internal oblique, and external oblique muscles during forced expiration in healthy adults

Abstract

Introduction: The purpose of this study was to characterize the rectus abdominis (RA), external oblique (EO), and internal oblique (IO)muscle activity level in healthy adults under expiratory resistance to expose the limitations of conventional expiratory muscle training. Methods: A total of 37 healthy adult subjects were randomly assigned to one of three groups: 30% of maximal expiratory intraoral pressure (30% PE max) group, 20% PE max group, and 10% PE max group. The RA, EO, and IO muscle activity level were measured during maximum voluntary contraction and during performed forced expiration under the assigned condition afrer measurement of maximal expiratory intraoral pressure (100% PE max) and muscle activity level during 100% PE max for all subjects. Results: At 100% PE max, the EO ( P P P P P P P P Conclusion: The two abdominal oblique muscles are the most active during forced expiration. Moreover, 30% PE max is the minimum intensity required to achieve significant muscle activity when expiratory resistance is applied, but the muscle activity obtained at 30% PE max is very small.