title: Dose-response relationship of baroreflex sensitivity and heart rate variability to individually-tailored exercise training in patients with heart failure.
abstract: BACKGROUND
  Heart Rate Variability (HRV) and Baroreflex Sensitivity (BRS) are impaired in patients with Chronic Heart Failure (CHF) and carry negative prognosis. Exercise training improves these parameters. However, the relationship between exercise training with HRV and BRS has been investigated without regard for individual training loads. We tested the hypothesis that in CHF patients changes in HRV and BRS are dose-response related to individual volume/intensity training load (TL).
  
  
  METHODS
  Twenty patients with stable postinfarction CHF under optimal medical treatment were randomized to either aerobic continuous training (ACT) or aerobic interval training (AIT) for 12weeks. Individualized TL was monitored by the Training Impulses (TRIMPi) method, which was determined using the individual HR and lactate profiling determined during a treadmill test at baseline. HRV (standard deviation of mean R-R interval) and BRS were assessed at rest and 3weeks apart, throughout the study.
  
  
  RESULTS
  HRV, BRS and R-R interval increased significantly with training, being very highly correlated to the dose of exercise with a second-order regression model (r(2) ranged from 0.75 to 0.96; P<0.001), resembling a bell-shaped in the ACT, and an asymptotic-shaped curve in the AIT groups, respectively. These changes were accompanied by a significant increase in functional capacity. No significant differences were detected between ACT and AIT in any variable.
  
  
  CONCLUSIONS
  These results suggest that improvements in HRV and BRS by exercise training in CHF patients are dose related to TL in a non-linear fashion on an individual basis, with optimal results at moderate doses of exercise.
authors.affiliation: Istituto di Ricovero e Cura a Carattere Scientifico San Raffaele Pisana, Rome, Italy. iellamo@med.uniroma2.
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Iellamo
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Manzi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Caminiti
authors.forename: Barbara
authors.initials: B
authors.lastname: Sposato
authors.forename: Michele
authors.initials: M
authors.lastname: Massaro
authors.forename: Anna
authors.initials: A
authors.lastname: Cerrito
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rosano
authors.forename: Maurizio
authors.initials: M
authors.lastname: Volterrani
mesh_terms: D000368:Aged; D017704:Baroreflex / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods*; D006333:Heart Failure / Q000503:physiopathology* / Q000628:therapy*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged