Acute effects of breathing exercises on diaphragmatic mobility and respiratory muscles activity in healthy adults

Objective : To investigate the differences between the breathing exercises sniff inspiration (SI), diaphragmatic breathing (DB), fractionated breaths (FB) and breathing from functional residual capacity (BFRC) in terms of their effect on diaphragmatic mobility and electrical activity of the sternocleidomastoid (SCM) and anterior scalene muscles in healthy adults in two positions: sitting and supported 30° trunk inclination. Methods : In a cross-sectional observational research, healthy adults of both sexes were recruited. Participants underwent anthropometric and spirometric assessment and their vital signs were measured. Diaphragmatic mobility (DM) was analyzed by ultrasound (US). Electrical activity of the sternocleidomastoid and anterior scalene muscles was assessed by electromyography (EM), in two positions: sitting and supported 30° trunk inclination. Results : A total of 30 individuals were assessed, 14 women and 16 men. Among the exercises studied, respiratory muscles were least used in DB for both positions and most used in BFRC. In regard to DM, the exercise that mobilized the diaphragm the most was BFRC in both studied positions, while DB caused the least mobilization of this muscle. Diaphragmatic mobility declined during trunk inclination at 30° and respiratory muscle electrical activity was lower when compared to the sitting position. Conclusion : In clinical practice, diaphragmatic breathing proved to be the exercise that least used the respiratory muscles. However, the BFRC with a 30° trunk inclination is the most recommended exercise when the objective is the mobilization of the diaphragm. It is important to know the muscle action during breathing exercises for a better prescription.