Earlobe Blood Flow Responses to Different Intensities of Inspiratory Resistance Loading in Healthy Young Men

Background and objectiveInspiratory resistance loading may alter peripheral circulation through changes in intrathoracic pressure and respiratory muscle pump activity.However, the relationship between inspiratory resistance intensity and peripheral blood flow remains unclear.This study aimed to investigate the response of earlobe blood flow (EBF) to varying intensities of inspiratory resistance loading in healthy young men. MethodsSixteen healthy young men performed multistep inspiratory resistance loading at 0%, 20%, 40%, 60%, and 80% of maximal inspiratory pressure (MIP) under incremental and decremental loading conditions on separate days.EBF was continuously measured, and the EBF ratio was calculated by dividing EBF at each loading intensity by resting EBF.The effects of loading intensity and loading condition were assessed using a linear mixed model.Changes in the EBF ratio across loading intervals were additionally evaluated using the slope (ΔEBF ratio/Δ% MIP). ResultsThe EBF ratio increased significantly with increasing loading intensity (F(4,135) = 11.89).The EBF ratio was significantly higher at 40%, 60%, and 80% MIP than at 0% MIP, whereas no significant difference was observed between 0% and 20% MIP.Neither the loading condition nor its interaction with loading intensity was significant.The slope of the EBF ratio did not differ significantly among loading intervals (F(3,105) = 1.29). ConclusionInspiratory resistance loading increased peripheral blood flow at low-to-moderate intensities, with the EBF response appearing to attenuate at approximately 40% MIP and above.