Abdominal muscle activity during breathing with and without inspiratory and expiratory loads in healthy subjects

Abstract Central Nervous System modulates the motor activities of all trunk muscles to concurrently regulate the intra-abdominal and intrathoracic pressures. The study aims to evaluate the effect of inspiratory and expiratory loads on abdominal muscle activity during breathing in healthy subjects. Twenty-three high school students (21.09±1.56 years; 8 males) breathed at a same rhythm (inspiration: two seconds; expiration: four seconds) without load and with 10% of the maximal inspiratory or expiratory pressures, in standing. Surface electromyography was performed to assess the activation intensity of rectus abdominis, external oblique and transversus abdominis/internal oblique muscles, during inspiration and expiration. During inspiration, transversus abdominis/internal oblique activation intensity was significantly lower with inspiratory load when compared to without load (p=0.009) and expiratory load (p=0.002). During expiration, the activation intensity of all abdominal muscles was significantly higher with expiratory load when compared to without load (p