Motor units involvement in diaphragm and intercostal muscles during supine and prone posture, and its relationship with oxygen saturation and perfusion index in healthy young female adults

Due to gravity and non-gravity variables, human posture influences the distribution of ventilation and perfusion. Gravity enhances the air exchange and posture has an impact on the respiratory muscles’ activity. The goal of the study was to determine the role of neuromuscular activities in respiratory muscles throughout various respiratory states and postures, as well as the degree to which two different lying positions affected the perfusion index (PI) and oxygen saturation (SpO2) level in young, healthy female adults. Thirty sedentary healthy female college students, age ranges from 18 to 25 years having no history of pulmonary or neuromuscular diseases voluntarily cooperated and participated in this study. Each participant’s diaphragm and intercostal muscles underwent surface electromyography in the supine and prone postures. The heart rate (HR), SpO2, and PI were measured. When in the supine position, the diaphragm and intercostal muscles both had greater mean root mean square and maximum voluntary contraction values, which is statistically significant (P < 0.05). However, HR, SpO2 level, and PI between supine and prone postures show negligible changes. According to this study, prone posture is advantageous to supine posture since it requires less motor unit activation for proper breathing. Contrarily, the increases in chest cavity capacity are insufficient for the healthy adult female’s calm breathing to result in an increase in SpO2 and PI.