Respiratory muscle training affects peripheral vascular function

Introduction Changes in breathing patterns, that are influenced by respiratory muscle training (RMT)(1), may also affect the autonomic balance by decreasing sympathetic drive and improve vascular function (2). Therefore, the aim of this study was to evaluate the efficacy of RMT on vascular function, assessed by flow mediated dilation (FMD), in young healthy subjects. Our hypothesis was that RMT could ameliorate both lung functions and brachial-artery FMD without affecting sympathetic and parasympathetic neural drive. Methods Twenty-three physically active participants were randomly assigned to an RMT group (TG: age 27±8 yrs, BMI 24±4 kg·m-2; RMT 3 times a week for 2 months, 15-30 minutes of progressive RMT assessed weekly) or to a sham group (SG: age 33±11 yrs, BMI 24±4 kg·m-2; 3 times a week for 2 months of RMT-Placebo). Maximal inspiratory mouth pressure (MIP) and maximum voluntary ventilation (MVV) were utilized to assess the pulmonary effects of RMT. Heart rate variability (HRV, the ratio between low and high frequency: LF/HF) was utilized to assess the autonomic balance. Vascular function was determined by measuring vessel vasodilation (%FMD), normalized by the shear rate (FMD/SR). Results After 2 months of RMT, MIP and MVV increased significantly by 25% and 8%, respectively, while in the SG, MIP and MVV didn’t change. In both TG and SG the changes in LF/HF were negligible. However, vascular function improved significantly only in TG (FMD/SR TG = -31 % FMD/SR; SG = -4 % FMD/SR). Discussion Data from the current study indicate a positive effect of RMT on both pulmonary and vascular function. However, contrary to our hypothesis, these positive results seem not primarily induced by adaptations of the autonomic balance. Therefore, physiological factors other than the modulation of sympathetic and parasympathetic nerve activity, seem positively triggered by the RMT (3). References