Influence of beta-blocker use on percentage of target heart rate exercise prescription.
BACKGROUND
Exercise is recommended for cardiac patients irrespective of beta-blockers. Percentages of maximal heart rate (%HRmax) and heart rate reserve (%HRR) are widely used to determine training intensities. The purpose of this study was to investigate the influence of chronic cardioselective beta blockade on the %HRmax and %HRR model.


METHODS
Ten healthy male subjects randomly received oral placebo or beta-blocker bisoprolol (5 mg/day) for 2 weeks using a double-blind, crossover design. In the second week, the subjects performed a cardiopulmonary exercise test until exhaustion to determine the aerobic (AeT) and anaerobic (AnT) threshold.


RESULTS
No significant differences were found for absolute and relative values of oxygen consumption, power output and ratings of perceived exertion at AeT, AnT and maximum workload. Mean HR was significantly (P<0.05) lower at rest (-15 +/- 5 bpm), AeT (-19 +/- 8 bpm), AnT (-22 +/- 10 bpm) and maximal workload (-19 +/- 11 bpm) with bisoprolol compared to placebo. Percentage of maximal heart rate (%HRmax) was significantly (P<0.05) reduced at rest (43 versus 39%), AeT (64 versus 60%) and AnT (86 versus 82%), a trend for a reduction was found for %HRR at AnT (75 versus 71%, P=0.07).


CONCLUSIONS
Exercise prescription using %HRmax or %HRR methods are of limited accuracy for patients taking beta-blockers. Although %HRmax and %HRR are easy to determine and therefore attractive, we suggest that the most precise exercise prescription would depend on AeT and AnT. Percentages of maximal oxygen consumption or maximal workload or ratings of perceived exertion may be suggested as a substitute. Alternatively, upper limits for %HRmax and %HRR should be lower for patients taking beta-blockers.
Wonisch
Manfred
M
Department of Internal Medicine, Karl-Franzens University Hospital, Graz, Austria. manfred.wonisch@uni-graz.at
Hofmann
Peter
P
Fruhwald
Friedrich M
FM
Kraxner
Wilfried
W
Hödl
Ronald
R
Pokan
Rochus
R
Klein
Werner
W
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000328:Adult; D017298:Bisoprolol / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects*; D010807:Physical Endurance / Q000187:drug effects*; D012016:Reference Values; D012129:Respiratory Function Tests
D000319:Adrenergic beta-Antagonists; D017298:Bisoprolol