G A Hetrick | PubMed Health

PubMed1986

Effects of beta-blockade on exercise capacity of trained and untrained men: a hemodynamic comparison.

To study the effects of cardiovascular fitness on hemodynamic responses to exercise during beta-adrenergic blockade (BAB), submaximal [60% of maximum O2 uptake (VO2max)] and maximal treadmill exercise data were collected in 11 trained (T, VO2max 63.3 ml X kg-1 X min-1, 26.8 yr) and 11 untrained (UT, VO2max 44.5 ml X kg-1 X min-1, 25.0 yr) male subjects. Subjects completed two maximal control tests followed by a randomized, double-blind series of maximal tests after 1-wk treatments with placebo (PLAC), propranolol (PROP, 160 mg/day, beta 1- and beta 2-blockade), and atenolol (ATEN, 100 mg/day, beta 1-blockade). Treatments were separated by 1-wk washout periods. At 60% of control VO2max T and UT subjects experienced no reductions in O2 uptake (VO2) with either drug. Submaximal heart rate (HR, beats/min) was 134.8 PLAC, 107.0 PROP, 107.9 ATEN (P less than 0.05 both drugs vs. PLAC) in T subjects and 141.1 PLAC, 106.1 PROP, and 105.0 ATEN (P less than 0.05 both drugs vs. PLAC) in UT subjects. Cardiac output (1/min) for T was 17.3 PLAC, 16.9 PROP, 16.5 ATEN (P less than 0.05 ATEN vs. PLAC in T only) and for UT it was 12.2 (PLAC), 11.7 (PROP), 11.5 (ATEN) (P less than 0.05 both drugs vs. PLAC in UT). Stroke volume increased from 129.8 ml (PLAC) to 158.6 (PROP) and 156.2 (ATEN) in T (P less than 0.05 both drugs vs. PLAC) and from 86.8 (PLAC) to 110.0 (PROP) and 109.8 (ATEN) (P less than 0.05 both drugs vs. PLAC) in UT. The increases in stroke volume (SV) were similar in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1985

Acute response to submaximal and maximal exercise consequent to beta-adrenergic blockade: implications for the prescription of exercise.

Forty-seven healthy male subjects, 17 to 34 years old, completed a test to exhaustion on a motor-driven treadmill to determine their maximal oxygen uptake. A second test was administered 2 days later during which the subject walked for 20 to 25 minutes at a steady-state level representing 60% of the maximal oxygen uptake as determined in the first test. The grade was then increased every 2 minutes until the subject reached the state of exhaustion. After the second test, the subjects were randomly assigned, in a double-blind manner, to either placebo, propranolol (160 mg/day), or atenolol (100 mg/day) treatment for 7 days. Exactly 1 week from the time of the second test, and 3 hours after the last medication, the subjects completed the final exercise test using the same treadmill protocol administered in the second test. Heart rate and systolic blood pressure at rest and during submaximal steady-state exercise were significantly reduced by both drugs, whereas diastolic pressure was unaffected. During submaximal steady-state exercise, cardiac output was reduced in both the placebo and atenolol groups, stroke volume was increased in both atenolol and propranolol groups, oxygen uptake was reduced in the atenolol group, pulmonary ventilation was reduced in both propranolol and atenolol groups, and the respiratory exchange ratio remained unchanged. With maximal exercise, treadmill time was significantly reduced with propranolol, pulmonary ventilation and heart rate were reduced significantly with both drugs, but maximal oxygen uptake remained unchanged. Thus, beta blockade does not appear to limit ability to exercise. However, there appears to be a significant advantage to using a cardioselective rather than a nonselective beta-blocking agent.

Adolescent↗