Influence of different postures on respiratory muscles activity during maximal voluntary ventilation in healthy adults

Background: Muscle activation can be altered by minor posture changes, which affect thoracoabdominal kinematics, quiet breathing, pulmonary function and volumes’ distribution in chest wall. Aim: to compare respiratory muscles activation during maximal voluntary ventilation (MVV) and slow vital capacity (SVC) in supine with a 45° inclination and sitting position by surface electromyography (sEMG) in healthy subjects. Methods: 20 healthy subjects (22,2±1,9 years; BMI 23,25±3,8 kg/m2) were assessed (scalene, sternocleidomastoid and abdominal rectum muscles) during MVV and SVC. Maneuvers and positions were randomized. All sEMG procedures were based on the Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles. Data were converted to root mean square (RMS). Additionally, MVV, SVC, tidal volume and respiratory rate were compared in each position. Statistical significance was set at p Results: There was greater ventilation in sitting position (MVV, p=0.003 and SVC, p=0.008). There was greater activation of scalene muscles in MVV (p=0.001) when compared to SVC in supine 45°. In sitting position, there were greater activation in all muscles in MVV compared to SVC (sternocleidomastoid, p=0.001; scalene, p=0.0001; abdominal, p=0.005). When compared both positions, there was greater activation of scalene in supine 45°(MVV,p=0.001;SVC,p=0.004) compared to sitting position. However, there was greater activation of abdominal rectum in sitting position in MVV (p=0.001). Conclusion: There was greater ventilation in sitting position and different pattern of respiratory muscles’ activation when compared MVV in two different positions in healthy subjects.