title: Potential effect of 6 versus 12-weeks of physical training on cardiac autonomic function and exercise capacity in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Exercise is an important part of chronic obstructive pulmonary disease (COPD) treatment. However, it is not know about the minimum effective time of physical training that could beneficially modify the cardiac autonomic modulation (CAM) and exercise capacity in these patients.
  
  
  OBJECTIVE
  To contrast the potential effects of a physical training program (PTP), for 6 versus 12 weeks, on CAM by linear and nonlinear heart rate variability (HRV) indices and exercise capacity in COPD patients.
  
  
  METHODS
  Prospective randomized controlled trial.
  
  
  METHODS
  Outpatient pulmonary rehabilitation.
  
  
  METHODS
  Twenty moderate-to-severe COPD patients were randomly assigned to either a training group (N.=10) or a control group (N.=10).
  
  
  METHODS
  HRV at rest and during submaximal test was determined by linear (rMSSD and SDNN) and non-linear indices (SD1, SD2 and sample entropy [SE]). In addition, key responses were obtained during cardiopulmonary exercise testing (CPET), the walking distance (WD) during the six minute walking test and submaximal constant speed testing (CST). PTP consisted of 30 minutes of aerobic exercise training on a treadmill, 3 times per week at 70% of CPET peak speed rate. Patients were evaluated on baseline, 6 and 12 weeks.
  
  
  RESULTS
  Significant improvements in HRV indices, WD, as well as, other physiological responses were observed after 6 weeks of the PTP and maintained until 12 weeks (P<0.05). However, after 12 weeks, the SD1 index demonstrated an additional improvement compared with 6 weeks (P<0.05). Peak oxygen uptake and dioxide carbon production improved only after 12 weeks (P<0.05). Interestingly, the 6th week-baseline delta (6th week-baseline) of WD, SDNN and SE were significantly higher than 12th week-6th week delta (P<0.05).
  
  
  CONCLUSIONS
  These results indicate that beneficial changes on cardiac autonomic modulation in conjunction with improvement in submaximal functional capacity occur in the first 6 weeks of PTP in moderate to severe COPD.
  
  
  CONCLUSIONS
  Short-term rehabilitation (6 weeks) is an effective sufficient time to beneficially modify important outcomes as cardiac modulation and exercise capacity in COPD patients.
authors.affiliation: Cardiopulmonary Physical Therapy Laboratory, Physical Therapy Department, Federal University of São Carlos São Carlos, São Paulo, Brazil - audrey@ufscar.br.
authors.forename: A
authors.initials: A
authors.lastname: Borghi-Silva
authors.forename: R G
authors.initials: RG
authors.lastname: Mendes
authors.forename: R
authors.initials: R
authors.lastname: Trimer
authors.forename: C R
authors.initials: CR
authors.lastname: Oliveira
authors.forename: G A
authors.initials: GA
authors.lastname: Fregonezi
authors.forename: V R
authors.initials: VR
authors.lastname: Resqueti
authors.forename: R
authors.initials: R
authors.lastname: Arena
authors.forename: L M
authors.initials: LM
authors.lastname: Sampaio-Jorge
authors.forename: D
authors.initials: D
authors.lastname: Costa
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000503:physiopathology*; D005080:Exercise Test / Q000379:methods; D005081:Exercise Therapy / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010043:Outcome and Process Assessment, Health Care / Q000706:statistics & numerical data; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000534:rehabilitation*; D013147:Spirometry; D013997:Time Factors; D014797:Vital Capacity / Q000502:physiology*