title: Influence of home-based telemonitored Nordic walking training on autonomic nervous system balance in heart failure patients.
abstract: BACKGROUND
  Rehabilitation positively affects the modulation of the autonomic nervous system (ANS). There are no papers evaluating the influence of Nordic walking training (NW) on ANS activity among chronic heart failure (CHF) patients. The aim of study was to assess the influence of NW on ANS activity measured by heart rate variability (HRV) and heart rate turbulence (HRT) in CHF patients and its correlation with physical capacity improvement measured by peak oxygen consumption (peak VO2 [ml/kg/min]) in the cardiopulmonary exercise treadmill test (CPET).
  
  
  METHODS
  The study group comprised 111 CHF patients (NYHA class II-III; ejection fraction (EF) ≤ 40%). Patients were randomized (2 : 1) to 8-week NW (five times weekly) at 40-70% of maximal heart rate (training group - TG) (n = 77), or to a control group (CG) (n = 34). The effectiveness of NW was assessed by changes (delta (Δ)) in peak VO2, HRV and HRT as a result of comparing these parameters from the beginning and the end of the programme.
  
  
  RESULTS
  Eventually, 36 TG patients and 15 CG patients were eligible for HRV and HRT analysis. In the TG low/high frequency ratio (LF/HF) decreased (1.9 ±1.11 vs. 1.7 ±0.63, p = 0.0001) and peak VO2 increased (16.98 ±4.02 vs. 19.70 ±4.36 ml/kg/min, p < 0.0001). Favourable results in CG were not observed. The differences between TG and CG were significant: Δpeak VO2 (p = 0.0081); ΔLF/HF (p = 0.0038). An inverse correlation was found between the decrease in ΔLF/HF and the increase in Δpeak VO2 (R = -0.3830, p = 0.0211) only in the TG. Heart rate variability did not change significantly in either group.
  
  
  CONCLUSIONS
  Nordic walking positively affects the parasympathetic-sympathetic balance in CHF patients, which correlates with the improvement in Δpeak VO2. No significant influence of NW on HRT was observed.
authors.affiliation: Telecardiology Centre, Institute of Cardiology, Warsaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Piotrowicz
authors.affiliation: Faculty of Physics, Warsaw University of Technology, Warsaw, Poland.
authors.forename: Teodor
authors.initials: T
authors.lastname: Buchner
authors.affiliation: Statistics Laboratory, Institute of Cardiology, Warsaw, Poland.
authors.forename: Walerian
authors.initials: W
authors.lastname: Piotrowski
authors.affiliation: Department of Cardiac Rehabilitation and Non-invasive Electrocardiology, Institute of Cardiology, Warsaw, Poland.
authors.forename: Ryszard
authors.initials: R
authors.lastname: Piotrowicz
keywords: autonomic nervous system; exercise training; heart failure; heart rate variability