[Purpose] The purpose of this study was to compare the activation of trunk muscles during end-inspiration of abdominal breathing among four different back exercise positions to investigate potential effects on the activation of trunk muscles. [Subjects] Sixty healthy male adults volunteered to participate in the study. [Methods] Each subject was instructed regarding abdominal breathing and the study procedure. While the maximal voluntary contraction and end-inspiration of abdominal breathing of individual muscles were being performed, the activity of the muscles was measured using surface electromyography. The activity of the muscles while performing end-inspiration of abdominal breathing was normalized to the percentage of maximal voluntary contraction (% MVC). [Results] Right and left erector spinae and external oblique showed significant differences among the positions between before and after end-inspiration of abdominal breathing(EIAB). The prone-on-elbows position demonstrated the greatest increase post-EIAB. [Conclusion] End-inspiration of abdominal breathing appears to be effective in the four different positions for activating the erector spinae and external oblique trunk muscles, but not rectus abdominis.