Effects of inspiratory muscle training on cardiac autonomic control

Abstract

Introduction: Inspiratory muscle training (IMT) has been used as a complementary method to improve the performance in athletes. However, there is no consensus about the effects of IMT on cardiac autonomic control assessed by heart rate variability (HRV). Objective: To identify the effects of IMT on cardiac autonomic control, assessed by the analysis of HRV, after active postural maneuver. Methods: Nine healthy recreational cyclists, all men with aged between 20-40 years, performed an IMT for 11 weeks, 1 hour/session, 3 times for week. The intensity was set at 60% of maximal inspiratory pressure, which was applied using an inspiratory resistor. The electrocardiogram was recorded continuously, in the supine and orthostatic postures (15 min each), before and after IMT. Spectral analysis of the HRV was performed, in which the high frequency (HF) and low frequency (LF) in normalized units (nu), represents vagal and sympathetic modulation, respectively. Paired t-test was used to compare the delta HRV indices (orthostatic minus supine), adopting p Results: There was observed increasing in sympathetic (ΔLFnu: 9.8 vs 24.3, p=0.007) and decreasing in parasympathetic modulation (ΔHFnu: -11.9 vs -24.3, p=0.010) after postural maneuver. Conclusions: IMT promoted increased cardiac autonomic response to postural maneuver, i.e., increased sympathetic modulation at orthostatic. This result reflects an improvement to the ability of this system to adapt to an external stimulus, which is important to athletes, once they are constantly exposed to physiological stress during sports practice. Moreover, these findings may guide future research in patients with postural hypotension. Support: Fapesp(2017/13402 0);CNPq(311938/2013-2).