Stroke volume during submaximal exercise in endurance-trained normotensive subjects and in untrained hypertensive subjects with beta blockade (propranolol and pindolol)

Treatment of hypertension in athletes: an evidence-based review

Hypertension is the most common cardiovascular condition in adults. It is also very common in athletes. When lifestyle changes fail, medications may be needed for the treatment of hypertension. When choosing a drug for antihypertensive therapy, providers should choose an agent that has favorable effects on blood pressure and minimal detrimental hemodynamic change during exercise. Evidence supports that the medications with the most favorable effects are angiotensin-converting enzyme inhibitors, calcium channel blockers, alpha-blockers, and cardiac-selective beta-blockers. The effects of diuretics are less desirable, and nonselective beta-blockers should be a last choice for hypertensive patients who are physically active.

Changes in stroke volume with beta-blockade before and after 10 days of exercise training in men and women

We sought to determine whether 10 days of training would be a sufficient stimulus for cardiac adaptations that would allow a greater compensatory stroke volume during beta-blockade. We also sought to determine whether men and women had a similar cardiac reserve capacity for increasing stroke volume with beta-blockade during submaximal exercise. Eight men (age 29 +/- 2 yr, mean +/- SE) and eight women (25 +/- 2 yr) cycled at 65% of peak O2 consumption (unblocked) under placebo-control and beta-blockade (100 mg atenolol) conditions performed on separate days. These tests were repeated at the same power output after training (10 consecutive days, 1 h of cycling per day). Before training, beta-blockade significantly (P < 0.05) decreased heart rate (HR) and cardiac output and increased stroke volume in both men and women. After training, the increase in stroke volume and decrease in HR with beta-blockade was significantly less while cardiac output was reduced more. There were no gender differences in the effects of beta-blockade on HR, stroke volume, or cardiac output. These data indicate that, during exercise with beta-blockade, exercise training for 10 days does not enhance the compensatory increase in stroke volume and that men and women have a similar cardiac reserve capacity for increasing stroke volume.

Reduced ambulatory heart rate response to physical work and complaints of fatigue among hypertensive males treated with beta-blockers

Treatment with beta-blockers affects oxygen metabolism and lipolysis during physical exertion. Together with possible central nervous system effects, this may impair the work capacity of treated hypertensive subjects. In a study of 1619 male employees, aged 45-64 years, mean resting and ambulatory heart rate (HR) and complaints of fatigue were compared between hypertensive workers treated with beta-blockers and untreated hypertensives and normotensives under low and high workload conditions. Treated hypertensives had lower mean resting HRs compared with normotensives and untreated hypertensives. Their change from resting to ambulatory HR during low and high workload was also lower than normotensives and untreated hypertensives, and they had higher fatigue scores than their untreated counterparts at both workload levels. The highest fatigue score was reported by treated subjects under high workload. These findings demonstrate a reduced HR response to physical work accompanied by more symptoms of fatigue during treatment with beta-blockers. When hypertensives are engaged in physically demanding work, other classes of antihypertensive therapy should be considered.

Effects of propranolol and pindolol on cardiac output during extended periods of low-intensity physical activity

The effects of a nonselective beta-adrenergic blocking agent with (pindolol) and without (propranolol) intrinsic sympathomimetic activity properties, compared with placebo-controlled conditions, on metabolic and cardiorespiratory function during long-duration (2 hours) physical activity were examined. After initial cardiorespiratory testing, subjects performed 2-hour walks at 25 and 45% of maximal oxygen consumption (VO2max) under each of the following 3 treatments: pindolol, propranolol and placebo. Medication distribution was randomized and double-blinded. A supine resting blood pressure and electrocardiogram were obtained before each exercise trial. Oxygen consumption, heart rate, stroke volume, cardiac output and blood pressure were determined after 5 minutes of quiet sitting and every 30 minutes during each 2-hour exercise trial. Cardiac output was not significantly different at rest or during exercise, comparing pindolol and propranolol with placebo conditions. Cardiac output tended to decrease over time earlier during propranolol treatment for the 25% VO2max trials in trained normotensive subjects than for the other treatments. Cardiac output decreased at approximately the same time across treatments during the 45% VO2max trials in trained normotensive and untrained hypertensive groups. Finally, owing to the observation that a reduction in cardiac output was delayed or prevented in trained normotensive subjects when compared with that in untrained hypertensives while exercising at 25% VO2max, developing a subject's cardiovascular fitness level may be important in the maintenance of cardiac output during extended periods of low-to-moderate physical activities while under the influence of beta-adrenergic blockade.

Effect of enhanced preload with head-out water immersion on exercise response in men with healed myocardial infarction

Head-out water immersion shifts venous blood to the central vasculature and heart and subsequently increases cardiac preload. In healthy men, cardiac output and stroke volume are greater during upright leg cycle exercise in water than on land. Heart rate is similar during work loads < 50% of peak oxygen consumption but is decreased in water at higher work intensities. To determine if men with myocardial infarction (MI) show a similar response, 15 men with a documented MI exercised upright on a leg cycle ergometer on land and immersed in water (31 +/- 1 degree C) to the level of the shoulders. Heart rate, cardiac output (carbon dioxide rebreathing procedure) and oxygen consumption were measured at rest and at work loads corresponding to approximately 40, 60 and 75% of peak oxygen consumption in both environments. At rest, cardiac output and stroke volume were elevated (p < 0.05) in water. During exercise, heart rate, cardiac output and stroke volume did not differ between water and land. When subjects were given beta-blocking medications (n = 8) and subjects with exercise-induced ST-segment depression (n = 5) were separately excluded from the analysis, water immersion still did not significantly change exercise responses. These results suggest that MI alters the normal cardiac response to increased preload during exercise. The alteration may involve reduced myocardial compliance or near-complete use of the Frank-Starling reserve, or both, during land exercise.

Effect of timolol on cardiopulmonary exercise performance in men after myocardial infarction

The effect of the nonselective beta blocker timolol on maximal cardiopulmonary exercise performance was evaluated in 28 men with previous myocardial infarction without effort angina (mean age 63 +/- 8 years). Patients were randomized to placebo or timolol (10 mg twice daily) for 4 weeks and then crossed over to the alternative therapy in a double-blind manner. At the completion of each treatment period, patients underwent symptom-limited maximal cardiopulmonary exercise on a cycle ergometer. Exercise time, heart rate, oxygen consumption (VO2), oxygen (O2) pulse and respiratory exchange ratio were measured at peak exercise and at a submaximal exercise level defined at a respiratory exchange ratio of 1.00. Timolol treatment reduced peak heart rate from 153 +/- 11 to 102 +/- 14 beats/min (-33%, p less than 0.001). Exercise time decreased from 680 +/- 91 to 633 +/- 78 seconds (-7%, p less than 0.001). Peak VO2 decreased from 25.3 +/- 4.7 to 21.4 +/- 3.5 ml/min/kg (-15%, p less than 0.001). O2 pulse increased from 12.9 +/- 1.9 to 16.7 +/- 2.3 ml/beat (+29%, p less than 0.001). Peak respiratory exchange ratio did not change significantly, indicating comparable effort. At submaximal exercise, defined at a respiratory exchange ratio of 1.00, there was no difference in exercise time between placebo and timolol. Heart rate decreased with timolol compared with placebo, from 126 +/- 16 beats/min by 31% (p less than 0.001), VO2 decreased from 18.5 +/- 4.3 ml/min/kg by 10% (p less than 0.001), O2 pulse increased from 11.5 +/- 2.0 ml/beat by 30% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)