title: Inspiratory muscle training reduces blood pressure and sympathetic activity in hypertensive patients: a randomized controlled trial.
abstract: BACKGROUND
  Autonomic imbalance, characterized by sympathetic hyperactivity and diminished vagal tone, is a known mechanism for essential hypertension. Inspiratory muscle training (IMT) demonstrates beneficial outcomes in a number of cardiovascular populations, which may potentially extend to patients with hypertension. The aim of this study was to further elucidate the effects of IMT on blood pressure and autonomic cardiovascular control in patients with essential hypertension.
  
  
  METHODS
  Thirteen patients with hypertension were randomly assigned to an eight-week IMT program (6 patients) or to a placebo-IMT (P-IMT, 7 patients) protocol. We recorded RR interval for posterior analysis of heart rate variability and blood pressure, by ambulatory blood pressure monitoring (ABPM), before and after the program.
  
  
  RESULTS
  There was a significant increase in inspiratory muscle strength in the IMT group (82.7 ± 28.8 vs 121.5 ± 21.8 cmH2O, P<0.001), which was not demonstrated by P-IMT (93.3 ± 25.3 vs 106.1 ± 25.3 cmH2O, P>0.05). There was also a reduction in 24-hour measurement of systolic (133.2 ± 9.9 vs 125.2 ± 13.0 mm Hg, P=0.02) and diastolic (80.7 ± 12.3 vs 75.2 ± 1.0 mm Hg, P=0.02) blood pressure, as well as in daytime systolic (136.8 ± 12.2 vs 127.6 ± 14.2 mm Hg, P=0.008) and diastolic (83.3 ± 13.1 vs. 77.2 ± 12.2 mm Hg, P =0.01) blood pressure in the IMT group. In relation to autonomic cardiovascular control, we found increased parasympathetic modulation (HF: 75.5 ± 14.6 vs. 84.74 ± 7.55 n.u, P=0.028) and reduced sympathetic modulation (LF: 34.67 ± 20.38 vs. 12.81 ± 6.68 n.u; P=0.005). Moreover, there was reduction of cardiac sympathetic discharge (fLF) in IMT group (P=0.01).
  
  
  CONCLUSIONS
  IMT demonstrates beneficial effects on systolic and diastolic blood pressure as well as autonomic cardiovascular control in hypertensive patients.
authors: Post Graduation Program in Health Sciences, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, RS, Brazil.
authors: Janaína Barcellos
authors: JB
authors: Ferreira
authors: Rodrigo Della Méa
authors: RD
authors: Plentz
authors: Cinara
authors: C
authors: Stein
authors: Karina Rabello
authors: KR
authors: Casali
authors: Ross
authors: R
authors: Arena
authors: Pedro Dal
authors: PD
authors: Lago
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D001945:Breathing Exercises / Q000379:methods*; D003964:Diaphragm / Q000294:innervation / Q000502:physiology*; D004311:Double-Blind Method; D000075222:Essential Hypertension; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology / Q000628:therapy*; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013564:Sympathetic Nervous System / Q000502:physiology*