The Effect of Beta-Adrenergic Blockade on Heart Rate Recovery from Exercise
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abstract
In patients treated with beta-adrenergic blocking agents, the practice of estimating exercise heart rate (HR) from postexercise pulse count may be invalid if beta-adrenergic blockade (BB) shortens the time course of heart rate recovery (heart rate recovery kinetics or HRK) after acute exposure to exercise. To determine the effect of nonspecific BB on HRK in nine healthy, drugfree men, HR was calculated from ECG recordings during submaximal (70% HR max reserve) cycle ergometer exercise and every 4 seconds for 2 minutes of recovery under both BB (80 mg propranolol) and placebo (PL) treatments (random order, double-blind); half-times of the HR recovery curves were subsequently calculated. Data analysis (2 x 31 randomized block factorial ANOVA; critical P<0.05) revealed that:(1) HR was significantly reduced by BB, (2) HR decreased significantly by the twelfth second of recovery, and (3) the treatment-by-time interaction term was not significant suggesting parallelism of the BB and PL HR recovery curves. Polynomial regression demonstrated that a second-order function provided optimal fit of the HRK data under both treatment conditions. In addition, HR recovery curve half-times were similar between treatments (ANOVA, P>0.05). Finally, HRs calculated from the last 15 seconds of exercise and the first 15 seconds of recovery were not significantly different; ingestion of BB did not affect this finding, although exercise and recovery HRs were reduced by BB treatment. These results demonstrate that HRK is unaffected by acute ingestion of nonspecific BB, and, if the pulse count is completed within the first 15 seconds after exercise cessation, estimating exercise HRs from postexercise pulse counts remains a valid procedure for patients receiving BB.
