No abstract

Controlled breathing maneuver is being widely applied for cardiovascular autonomic control evaluation and cardiac vagal activation through reduction of breathing rate (BR). However, this maneuver presented contradictory results depending on the protocol and the chosen BR. These variations may be related to the individual intrinsic profile baseline sympathetic tonus, as described before by others. In this study, we evaluated the effect of controlled breathing maneuver on cardiovascular autonomic control in 26 healthy subjects allocated into two protocols: (1) controlled breathing in three different rates (10, 15, and 20 breaths/min) and (2) controlled breathing in rates normalized by the individual spontaneous breathing rate (SBR) at 100, 80, 70, and 50%. Our results showed autonomic responses favorable to vagal modulation with the lower BR maneuvers. Nevertheless, while this activation was variable using the standard protocol, all participants of the normalized protocol demonstrated an increase of vagal modulation at 80% BR (HFnu 80 = 67.5% vs. 48.2%, p < 0.0001). These results suggest that controlled breathing protocols to induce vagal activation should consider the SBR, being limited to values moderately lower than the baseline.

BackgroundPhysical exercise reduces glucose levels and glucose variability in patients with type 2 diabetes. Acute inspiratory muscle exercise has been shown to reduce these parameters in a small group of patients with type 2 diabetes, but these results have yet to be confirmed in a well-designed study. The aim of this study is to investigate the effect of acute inspiratory muscle exercise on glucose levels, glucose variability, and cardiovascular autonomic function in patients with type 2 diabetes.Methods/designThis study will use a randomized clinical trial crossover design. A total of 14 subjects will be recruited and randomly allocated to two groups to perform acute inspiratory muscle loading at 2 % of maximal inspiratory pressure (PImax, placebo load) or 60 % of PImax (experimental load).DiscussionInspiratory muscle training could be a novel exercise modality to be used to decrease glucose levels and glucose variability.Trial registrationClinicalTrials.gov NCT02292810.

BackgroundRespiratory exercises have proven to be an effective non-pharmacologic intervention for the treatment and prevention of hypertension 1 and psychological states, such as anxiety and depression. 2 However, not much has been demonstrated concerning respiratory patterns that could be considered critical parameters for health issues.Most respiratory evaluations are related to pulmonary function (spirometry) or respiratory muscle strength (maximal inspiratory and expiratory pressure) and made by means of a mouth device that could interfere with most people's natural breathing. 3 Abdominal cavity and rib cage movements involved in respiration have the potential to be evaluated (piezoelectric belts), but