title: Influence of β-blockers on heart rate recovery and rating of perceived exertion when determining training intensity for cardiac rehabilitation.
abstract: BACKGROUND
  The influence of β-blockers on heart rate recovery (HRR) and rating of perceived exertion (RPE) during Phase I cardiac rehabilitation (CR) for patients with a recent episode of acute myocardial infarction (AMI) is not clear.
  
  
  METHODS
  From October 2009 to July 2011, 105 patients with a recent episode of AMI who received a successful percutaneous coronary intervention were recruited into this study. Before entering Phase II CR, each patient underwent a cardiopulmonary exercise test (CPET), where RPE was assessed every minute and related parameters were recorded.
  
  
  RESULTS
  The participants entering CR had relatively low mean peak oxygen consumption (VO2max). However, the peak heart rate and VO2max were lower in those taking β-blockers. The RPE value at the ventilatory threshold (VT) was significantly higher (12.7 ± 1.7) in participants who were taking β-blockers relative to those who were not (11.5 ± 1.4). The HRR value was lower (12.5 ± 8.8) in participants who were taking β-blockers relative to those who were not (17.0 ± 9.1).
  
  
  CONCLUSIONS
  These findings suggest that use of β-blockers increased the RPE value at the VT. In addition, HRR was attenuated by β-blockers. In patients who do not undergo CPET, the use of β-blockers should be taken into consideration when using RPE for the initial exercise prescription to determine training intensity.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan, ROC; Department of Physical Medicine and Rehabilitation, School of Medicine, Tzu Chi University, Hualien, Taiwan, ROC; Department of Physical Medicine and Rehabilitation, Taichung Veterans General Hospital, Taichung, Taiwan, ROC. Electronic address: tsaisenwei@gmail.com.
authors.forename: Sen-Wei
authors.initials: SW
authors.lastname: Tsai
authors.affiliation: Department of Physical Medicine and Rehabilitation, Chung Shan Medical University Hospital, Taichung, Taiwan, ROC; School of Medicine, Chung Shan Medical University, Taichung, Taiwan, ROC; School of Occupational Therapy, Chung Shan Medical University, Taichung, Taiwan, ROC.
authors.forename: Yu-Hui
authors.initials: YH
authors.lastname: Huang
authors.affiliation: Department of Physical Medicine and Rehabilitation, Taichung Veterans General Hospital, Taichung, Taiwan, ROC.
authors.forename: Yan-Wen
authors.initials: YW
authors.lastname: Chen
authors.affiliation: Cardiovascular Center, Taichung Veterans General Hospital, Taichung, Taiwan, ROC.
authors.forename: Chih-Tai
authors.initials: CT
authors.lastname: Ting
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology*; D010101:Oxygen Consumption / Q000187:drug effects; D005082:Physical Exertion / Q000187:drug effects*
chemical_list: D000319:Adrenergic beta-Antagonists
keywords: acute myocardial infarction; cardiac rehabilitation; rating of perceived exertion; β-blocker