Exercise in Treating Hypertension

Tailoring Therapies for Active Patients

Jirayos Chintanadilok, MD
David T. Lowenthal, MD, PhD

Exercise and Sports Cardiology Series
Editor: Paul D. Thompson, MD

THE PHYSICIAN AND SPORTSMEDICINE - VOL 30 - NO. 3 - MARCH 2002

In Brief: Even mild-to-moderate elevations in blood pressure dramatically increase the risk of left ventricular hypertrophy, stroke, and renal disease. Although antihypertensive drugs can reduce blood pressure, their side effects and cost have stimulated a search for alternatives. Nonpharmocologic interventions can serve as definitive therapy for selected patients and as adjunctive therapy for many hypertensive patients. Patients with secondary hypertension should be treated directly and may not derive as much benefit from exercise. Low-to-moderate intensity aerobic exercise can help mildly hypertensive patients and reduce the drug dosage of those more severely affected. For active patients who require medication, regimens can be tailored to minimize adverse drug effects.

Hypertension is defined as blood pressure equal to or greater than 140/90 mm Hg with or without antihypertensive medication use, and approximately 50 million Americans are hypertensive.¹ Individuals who have blood pressure that is more than 160/95 mm Hg have an annual incidence of coronary artery disease (CAD), congestive heart failure, intermittent claudication, and stroke that is up to to three times higher than normotensive persons.² They also have an exercise capacity about 30% less.³

Regular moderate aerobic activity can safely lower blood pressure^4-12 and reduce the risk of future hypertension in children.^13-15 Exercise recommendations are based on the sixth National Report.⁴ The intensity can generally be increased without an extensive medical evaluation as long as symptoms of overt cardiac, neurologic, and musculoskeletal diseases are not provoked by walking. Physicians may encounter patients with secondary hypertension, such as those with renal artery stenosis, coarctation of the aorta, adrenocortical or benign tumors, or unexplained hypokalemia, and should treat them directly; these patients may not benefit as much from exercise. Tailored exercise prescriptions can lower blood pressure in hypertensive patients, including those on medication.

Nonpharmacologic Blood Pressure Reduction

All current guidelines recommend exercise as an adjunctive nonpharmacologic intervention for mild hypertension, and antihypertensive medications for more severe disease. The data from the Hypertension Detection and Follow-up Program indicate that pharmacologic management reduces mortality in hypertensive patients.¹⁶ The study also strongly supports assessing mildly hypertensive patients individually and prescribing drugs according to composite risk factors rather than solely on blood pressure. Some patients with mild hypertension have a low risk of developing cardiovascular diseases and can safely be spared antihypertensive drugs. For others, medications may have no benefit¹⁷ or increase mortality.¹⁸

Preventing coronary heart disease among hypertensive patients requires a combination of nonpharmacologic treatments that seek to decrease atherosclerosis. Lifestyle interventions include losing weight, exercising more, reducing dietary salt, reducing stress, and lowering alcohol consumption. Currently, aerobic exercise and diet-induced weight loss have emerged as the most effective and physiologically desirable approaches.¹⁹ A large clinical trial²⁰ has demonstrated that mild-to-moderate exercise and weight loss can lower systolic and diastolic blood pressure in both men and women, although another study²¹ showed that exercise and diet-induced weight loss had no additive effect.

Many studies^22-26 have validated exercise for treating high blood pressure. Exercise not only reduces blood pressure, it also lowers levels of low-density lipoprotein cholesterol, reduces insulin resistance and glucose intolerance, and often is associated with reduced body weight.^27,28

The Sixth Joint National Committee guidelines⁴ for initiating drug therapy should be followed once low-risk patients have undergone 6 to 12 months of nonpharmacologic approaches. Physicians should give a detailed exercise prescription and provide regular encouragement and follow-up to improve patients' compliance and motivation.

How to Prescribe Exercise

Patient selection and evaluation. All patients with controlled hypertension should participate in exercise training (table 1). Exercise can be used with other nonpharmacologic interventions, and in uncomplicated mild-to-moderate hypertensive patients without antihypertensive medications. Patients with cardiovascular complications (eg, target-organ damage or diabetes) or who are elderly require antihypertensive drugs.⁴ Patients with blood pressure greater than 180/105 mm Hg should add endurance exercise training only after medication controls their blood pressure. The exercise may reduce blood pressure further, decrease the dosage of antihypertensive agents required, and attenuate the risk of premature mortality.

TABLE 1. Exercise Prescriptions for Selected Groups of Patients Who Have Borderline-to-Moderate-Hypertension

Exercise substantially reduced the required doses of antihypertensive drugs.^31,32 Patients with unilateral renovascular disease and controlled blood pressure can exercise without further damage to the kidneys. Jessup et al³³ have shown that healthy elderly persons can endure 4 months of exercise training with no decrement in renal function.

Exercise Testing and Monitoring

The role of exercise testing is not settled. Most patients require only a good clinical evaluation. Sudden cardiac death is the most worrisome potential complication of exercise, but the absolute risk is very minimal (see "Cardiovascular Risks of Exercise: Avoiding Sudden Death and Myocardial Infarction). CAD and hypertrophic cardiomyopathy, the most common causes of sudden death in the old and young, respectively, can be associated with hypertension and can be detected by careful history taking, physical examination, resting ECG, and an echocardiogram.

The American College of Sports Medicine recommends that an exaggerated blood pressure response to exercise should not be used as a screening test to identify those at high risk of developing hypertension. However, exercise test information does provide some indication of risk stratification for the patient with a blood pressure response above the 85th percentile.³⁴

Graded exercise stress tests (GXTs) can gauge the magnitude of blood pressure response during exercise and rate of recovery, as well as the provocation of arrhythmias during the test. Physicians often recommend GXTs for adults older than 40 who plan to begin an exercise training program (see table 1).

Most patients with mild hypertension and no other cardiovascular disease risk factors can start a walking exercise program without a maximal GXT, but patient health and age determine the test required. Patients with moderate-to-severe hypertension who show ECG evidence of left ventricular hypertrophy should have a GXT and probably myocardial radioimaging.³⁴ Diabetic hypertensive patients should be evaluated carefully with exercise testing because they have a high incidence of silent myocardial infarction. A treadmill GXT should use protocols that maintain a constant walking speed for accurate blood pressure measurement during the exercise.³⁵

Exercise to Meet Patient Needs

Endurance exercise is the preferred type for hypertensive patients. The blood pressure response to aerobic exercise depends on the activity.

Aerobic exercise. Most studies have examined walking, running, or cycling. Walking and running do not cause a sustained increase in blood pressure and perhaps represent the most suitable endurance exercises for hypertensive patients. Some patients exhibit higher blood pressure with swimming than with running at comparable heart rates but have smaller cardiopulmonary effects. Moderate swimming (30- to 45-minute sessions, 3 days/wk) can lower systolic but not diastolic blood pressure at rest.³⁶ Swimming can be an alternative exercise for patients who are obese, have exercise-induced asthma, or have orthopedic injuries.

Vigorous activities done with rhythmic high force, such as sprinting or rowing, are unsuitable for hypertensive patients. Downhill skiing can elevate blood pressure, and mountain sports may exaggerate an elevated blood pressure response from the cold and decreased partial pressure of oxygen.³⁷

Tai chi chuan. This 1,000-year-old martial art is a low-impact exercise that combines slow, rhythmic movements with changes in direction, plane, and center of balance. It is simple and well tolerated by sedentary older persons. In one trial,³⁷ a tai chi program reduced patients' blood pressure to about that achieved by moderate-intensity aerobic exercise, but it did not change maximal aerobic capacity and produced fewer changes in other measures of physical activity. No large-scale, randomized, controlled clinical trial has documented its cardiovascular effects.

Exercise intensity, frequency, and duration. No specific guidelines delineate exercise intensity and frequency, but little evidence justifies high-intensity exercise (>70% VO₂max) for lowering blood pressure.²⁵

Endurance exercise training at 40% to 70% VO₂max may be as or more effective than high-intensity exercise in lowering blood pressure in hypertensive subjects.³⁸ Intervention studies and the World Hypertension League consensus statement³⁹ suggest that patients exercise at 50% to 85% maximum oxygen uptake for 20 to 60 minutes, 3 to 5 days per week. Alternatively, exercise heart rate should be within 50% to 70% of its predicted maximum (220 2 age in years). Lower-intensity activity requires longer duration: Exercise at 60% to 70% of maximum work capacity, 45 minutes per session, 3 days per week for 1 month, has the same hypotensive effect as exercise at 47% maximum work capacity, 60 minutes per session, 3 days per week, for 2.5 months.^39-42 Low-intensity (about 50% maximum oxygen consumption) exercise is also more beneficial than higher-intensity exercise for addressing stress. Exercise must produce a conditioning effect, usually three or four exercise sessions of 30 to 45 minutes each week at 60% to 70% of maximal heart rate.

Exercise training programs longer than 10 weeks appear to reduce systolic blood pressure by 1 to 2 mm Hg and diastolic blood pressure by 2 to 2.5 mm Hg more than shorter-duration programs.²⁴ Generally, no further blood pressure reduction occurs after 3 months of training, except in rare instances.^42,43 The program should be at least 1 to 3 months to reach the stable stage, and training should be maintained indefinitely, because the hypotensive effect persists only as long as regular endurance exercise is maintained.

Drug Therapy for Active Hypertensive Patients

There is no "best" medication for the active hypertensive patient. Physicians should tailor medication to the patient's status.

Hypertension only. The active hypertensive patient of any age could take a thiazide diuretic, 12.5 mg to 25 mg daily, and a potassium supplement. Diuretics are effective and inexpensive. Thiazides are useful in hypertensive postmenopausal women with osteoporosis because these drugs decrease urinary calcium loss. All of the other classes of antihypertensive drugs are effective in controlling blood pressure and, although they are expensive, can be used as monotherapy for this type of hypertensive patient. Patients who need to take a beta-blocker can gradually train through the blunted cardiovascular response to aerobic exercise. Beta-blockers are also effective and inexpensive.

Hypertension with other diseases. Hypertensive patients who have other diseases require more specific treatment. For example, those with CAD would benefit from either a calcium-entry blocker or a beta-blocker; a diabetic patient would need an angiotensin-converting enzyme (ACE) inhibitor; and a patient who coughs while on an ACE inhibitor but has left ventricular hypertrophy should take an angiotensin-2-receptor blocker. Active elderly hypertensive men with prostatism would obtain blood pressure control as well as relief from outlet obstruction with a peripheral alpha-blocker (eg, terazosin, doxazosin mesylate). If these drugs cause dizziness or orthostatic hypotension, the alpha-blocker tamsulosin can be given with any other low-dosage antihypertensive drug.

Antihypertensive Therapy and Exercise Performance

Antihypertensive treatment for athletes and other physically active people seeks to control blood pressure without compromising actual exercise performance (or performance surrogates such as increases in heart rate, stroke index, and cardiac index). No absolute contraindications exist for using any drug class in such patients, although certain classes are preferred or better tolerated (see "Exercise and Antihypertensive Medications in Patients with Dyslipidemias").

Diuretics. These drugs limit plasma volume expansion required for aerobic training.⁴⁴ Thiazides depress blood pressure during exercise by decreasing peripheral resistance and plasma volume. Long-term thiazide use does not reduce cardiac output. The effects of loop-blocking drugs, such as furosemide, on exercise have not been well studied, but these drugs are used infrequently for controlling blood pressure because they have a short duration.

Hypokalemia is the most worrisome, yet manageable, problem in active individuals taking diuretics. In hypokalemic states, muscle blood flow decreases, and during exercise skeletal muscle necrosis may occur, resulting in rhabdomyolysis and acute renal failure. To ensure against potassium loss, patients taking diuretics should receive supplements.

Beta-blockers. Unlike ACE inhibitors and calcium channel blockers, beta-blockers blunt exercise-mediated increases in heart rate and cardiac output and may reduce exercise performance. This response is more profound with nonselective beta blockade (eg, propranolol), and is greater with chronic than with acute dosing.^45,46 Nevertheless, training intensity can be estimated using a scale of perceived exertion in patients taking beta-blockers.^47,48

VO₂ Comparison of patients taking propranolol, metoprolol, or placebo showed that in graded exercise tests, heart rate, systolic blood pressure, and VO₂max were reduced at maximum exertion, although no major changes were seen in the anaerobic threshold.^48,49 These exercise effects were dose related. There was no difference between the placebo group and patients taking 40 mg/day of propranolol, but those who took 160 mg/day or 320 mg/day significantly reduced their heart rate response and VO₂max. Metoprolol users had less blunting of the heart rate. Beta-blockers may cause exertional fatigue and elevated serum potassium concentrations during exercise to levels greater than those seen with exercise alone, but clinical consequences in exercise are remote.⁴⁶

Patients who have chronic lung disease with bronchospasm should avoid all beta-blockers. Exercise-induced asthma should be managed with cromolyn sodium, and selective beta-blockers, if indicated, can be used cautiously.

Virtually all studies of the effects of beta-blockers on exercise and how exercise alters the pharmacodynamics and drug kinetics have been done in relatively young people.⁴⁸ In one study⁴⁹ of healthy elderly volunteers who performed 4 months of dynamic exercise training, researchers saw no changes in propranolol's kinetic or protein-binding characteristics.

Vasodilators. Alpha-adrenergic blocking drugs. Prazosin, terazosin, and doxazosin do not suppress cardiac output or exercise capacity⁴⁴ and are excellent choices for athletes and other active patients. Prazosin decreases mean arterial blood pressure and total peripheral resistance at rest and with dynamic work. In contrast to hydralazine hydrochloride, prazosin blunts any reflex increase in heart rate or pressor response during isometric exercise.⁵⁰

Calcium channel blockers. In normal, active persons, verapamil, diltiazem, and nifedipine exert adequate control during exercise, although a mild blunting of the diastolic blood pressure response to handgrip was observed with verapamil.⁵¹ In hypertensive patients, verapamil and nifedipine reduce systolic and diastolic blood pressure during exercise, perhaps by reducing systemic vascular resistance.^52,53 There is no change in serum potassium levels between patients taking verapamil or nifedipine and those taking a placebo during isometric exercise.⁵¹

These medications are beneficial for patients who are not good candidates for beta-blockers, including those with bronchospastic pulmonary disease or type 1 diabetes mellitus, and those in whom beta-blockers induce fatigue or are contraindicated.

ACE inhibitors. These drugs reduce systolic and diastolic blood pressure during exercise.⁴⁷ A review⁵⁴ of early studies with the angiotensin-2 partial antagonist, saralasin, also showed the same effect. In the absence of diabetes mellitus of either type, ACE inhibitors do not influence microalbuminuria observed with prolonged vigorous physical activity. Elevated serum potassium levels from ACE inhibitors and exercise do not have clinical consequences because the drug does not blunt catecholamine action, so potassium can move intracellularly. This contrasts with beta-blockers, which block catecholamine action to drive potassium back into the cell.

The overall responses to dynamic and static activities are not impaired with these drugs or the angiotensin-2-receptor blockers, losartan and valsartan.⁵⁵

Central alpha agonists. Methyldopa in mildly hypertensive patients may decrease the blood pressure response but does not alter the heart rate response to exercise.^56,57 Clonidine reduces both blood pressure and heart rate at rest and very slightly during exercise and produces an acute vagally mediated decrease in cardiac output that does not persist with chronic use.^58,59 Transdermal clonidine patches were superior to oral atenolol in improving aerobic conditioning in a group of relatively young, mildly hypertensive patients.⁶⁰

Neither clonidine nor methyldopa augment the changes in serum potassium, renin, and aldosterone levels that are normally observed in healthy persons who exercise⁶¹ or in patients who take beta-blockers.⁴⁸

The Road Ahead

Physical activity in the control and prevention of hypertension among adults has so many advantages that physicians should not hesitate to recommend exercise for management. Aerobic exercise or endurance training at low-to-moderate intensity is the exercise of choice, and emerging modes, such as circuit weight training and tai chi, are promising but require further study.

Antihypertensive medications such as diuretics and beta-blockers can interfere with exercise performance, but others, such as ACE inhibitors, alpha-adrenergic blockers, and calcium channel blockers, do not and are well tolerated by active individuals. A combination of nonpharmacologic interventions, such as exercise and weight loss, may provide sufficient benefit to decrease cardiovascular risks independent of drug treatment.

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Dr Chintanadilok is a fellow in the Geriatric Research, Education and Clinical Center (GRECC) at the Veterans Affairs Medical Center and the University of Florida College of Medicine in Gainesville. Dr Lowenthal is director of GRECC and professor of medicine, pharmacology, and exercise science at the University of Florida College of Medicine. Address correspondence to David T. Lowenthal, MD, PhD, Director, Hypertension Section, Division of Nephrology, University of Florida, Dept of Veterans Affairs Medical Center, 1601 Archer Rd, Gainesville, FL 32608-1197; e-mail to dlowenth@college.med.ufl.edu.

Disclosure information: Dr Lowenthal discloses no significant relationship with any manufacturer of any commercial product mentioned in this article. No drug is mentioned in this article for an unlabeled use.