Changes in training posture induce changes in the chest wall movement and respiratory muscle activation during respiratory muscle training.

Postural changes induce changes in chest wall kinematics and eventually pulmonary function, and affect chest wall shape and chest motion. This study aimed to examine the effects of postural change on changes in the chest wall during respiratory muscle training. Using a repeated measures design, this study followed 13 healthy adults (13 men; mean age, 23.73 years). All participants performed four postures (neutral, full trunk rotation, half-range trunk rotation, and lateral ribcage shift postures) during respiratory muscle training. The chest wall movement during the four postures was measured using a three-dimensional motion-analysis system during respiratory muscle training. Surface electromyography data were collected from the diaphragm and sternocleidomastoid muscles, and the asymmetric ratio of muscle activation was calculated based on the collected data. The chest wall movements of the upper costal and middle costal region were greater in the neutral posture than in the full rotation, half rotation, and lateral ribcage shift postures (<0.05). The respiratory muscle activation on diaphragm of left was greater in the full rotation posture than in the neutral posture, half rotation, and lateral ribcage shift postures (<0.05). The asymmetric ratio of muscle activation was greater in the full rotation posture than in the neutral posture, half rotation, and lateral ribcage shift postures (<0.05). This study verified that postural change during respiratory muscle training may affect chest wall movement and muscle activation. Thus, this study recommends respiratory muscle training to be performed in neutral posture.