Motor Unit Involvement of Diaphragm and Intercostal Muscles in Eupneatachypnea and Bradypnea of Young Female Sedentary Adults

Purpose: The involvement of motor units duringtheir activities in primary and secondary musclesrapidly becomes prominent as a diagnostic tool forpathological conditions. But no research has beenpublished so far indicating the involvement of motorunits during physiological circumstances likeEupnea, Bradypnea, and Tachypnea. These findingswould help to determine the neuromuscularmechanism of respiratory mechanics inphysiological situations and to compare it withclinical conditions related to respiratory muscles.Aim of the study: The experimental findings wouldhelp to determine the neuromuscular mechanism ofrespiratory mechanics in physiological situationsand to compare it with clinical conditions related torespiratory muscles.Materials and methods: Thirty healthy sedentaryadult females participated in this investigation. TheTachypnea and Bradypnea were deliberatelyachieved by asking them to hyperventilate withshallow breaths and to hold their breath for a periodin a supine posture accordingly. The participation ofmotor units and force generated in the diaphragmand intercostal muscles were assessed by surfaceelectromyography (sEMG).Results: The motor unit activities for three varioussituations such as silent breathing reduced breathing,and fast breathing rates significantly vary with eachother in both the primary respiratory muscles(p<0.05). But there was insignificant variation inmotor unit discharges between Eupnea andbradypnea of both muscles.Conclusions: In supine posture during Tachypnea,the quick and enhanced expansion of the thoraciccavity requires more motor unit activation in thediaphragm and intercostal muscle thus suggestinghigher involvement. In Eupnea and Bradypneavirtually equal participation of both muscles wasdiscovered. The modest increase in intercostal motorunit discharge in bradypnea than Eupnea might beowing to the larger extension of the intercostalmuscle during bradypnea than the diaphragm does.