Static exercise in untreated systemic hypertension

An evidence-based guide to the efficacy and safety of isometric resistance training in hypertension and clinical implications

More than 30 randomized controlled trials, supported by individual patient-level and group-level meta-analyses and a Delphi analysis of expert opinion, unequivocally show isometric resistance training (IRT) elicits antihypertensive benefits in healthy people and those with chronic illness. We aim to provide efficacy and safety evidence, and a guide for IRT prescription and delivery. Recommendations are made for the use of IRT in specific patient populations and appropriate methods for IRT delivery. Published data suggest IRT consistently elicits mean blood pressure reductions of 7.4/3.3 mmHg systolic blood pressure/diastolic blood pressure, equivalent to antihypertensive medication monotherapy. Blood pressure reductions of this size are associated with an approximate 13% to 22% reduction in major cardiovascular events. Moreover, IRT is safe in a range of patient populations. We suggest that IRT has the greatest potential benefit when used as an antihypertensive therapy in individuals unwilling and/or unable to complete aerobic exercise, or who have had limited adherence or success with it; individuals with resistant or uncontrolled hypertension, already taking at least two pharmacological antihypertensive agents; and healthy or clinical populations, as an adjunct to aerobic exercise and dietary intervention in those who have not yet attained control of their hypertension. IRT is efficacious and produces clinically meaningful blood pressure reductions (systolic blood pressure, 7 mmHg; diastolic blood pressure, 3 mmHg). IRT is safe and typical program delivery requires only about 17 min weekly. IRT should be used as an adjunct to other exercise modalities, in people unable to complete other types of exercise, or in resistant hypertension.

Evidence for the role of isometric exercise training in reducing blood pressure: potential mechanisms and future directions

Hypertension, or the chronic elevation in resting arterial blood pressure (BP), is a significant risk factor for cardiovascular disease and estimated to affect ~1 billion adults worldwide. The goals of treatment are to lower BP through lifestyle modifications (smoking cessation, weight loss, exercise training, healthy eating and reduced sodium intake), and if not solely effective, the addition of antihypertensive medications. In particular, increased physical exercise and decreased sedentarism are important strategies in the prevention and management of hypertension. Current guidelines recommend both aerobic and dynamic resistance exercise training modalities to reduce BP. Mounting prospective evidence suggests that isometric exercise training in normotensive and hypertensive (medicated and non-medicated) cohorts of young and old participants may produce similar, if not greater, reductions in BP, with meta-analyses reporting mean reductions of between 10 and 13 mmHg systolic, and 6 and 8 mmHg diastolic. Isometric exercise training protocols typically consist of four sets of 2-min handgrip or leg contractions sustained at 20-50 % of maximal voluntary contraction, with each set separated by a rest period of 1-4 min. Training is usually completed three to five times per week for 4-10 weeks. Although the mechanisms responsible for these adaptations remain to be fully clarified, improvements in conduit and resistance vessel endothelium-dependent dilation, oxidative stress, and autonomic regulation of heart rate and BP have been reported. The clinical significance of isometric exercise training, as a time-efficient and effective training modality to reduce BP, warrants further study. This evidence-based review aims to summarize the current state of knowledge regarding the effects of isometric exercise training on resting BP.

Muscle fibre composition in relation to blood pressure response to isometric exercise in normotensive and hypertensive subjects

A positive relationship was demonstrated between the blood pressure and the fibre composition of the vastus muscle at rest in 17 hypertensive and 17 age- and sex-matched normotensive subjects. The hypertensive group had a higher proportion of fast twitch (FT) fibres (p less than 0.1). The circulatory response was measured during isometric exercise (IE) and cold pressor test (CPT). During IE the blood pressure increase was positively related to the percentage of FT fibres. No such relationship was demonstrated during CPT. It was thus found, particularly in hypertensive subjects, that an individual's muscle fibre profile is of importance for the blood pressure response during IE.

Influence of cardiovascular diseases upon the results of the cardiovascular reflex tests in diabetic and nondiabetic subjects

Cardiovascular reflex tests are used to assess cardiac autonomic neuropathy in diabetes mellitus. Cardiovascular diseases (CVD) are known to alter baroreflex mechanisms. Diabetic patients are at a high risk for cardiovascular complications. In order to prove whether cardiovascular diseases reduce the diagnostic value of the cardiovascular reflex tests in diabetic autonomic neuropathy unselected groups of 274 nondiabetic and 103 diabetic patients were studied: E/I, 30/15, and Valsalva ratios, sustained handgrip test and blood pressure response to standing. Both groups were subdivided into young (less than or equal to 45 years) and older (greater than 45 years) patients and into subjects with and without CVD. In young nondiabetic patients with CVD, E/I and Valsalva ratios were significantly lower than in those without CVD. In young diabetic patients with CVD, only E/I ratios were significantly reduced compared to those without CVD. The tests reflecting sympathetic nerve function did not differ between patients with and without CVD, neither in the nondiabetic nor in the diabetic subjects. In the older nondiabetic and diabetic patients, cardiovascular reflexes were generally impaired, but did not show any difference between subjects with and without CVD. In young diabetic patients suffering from CVD, the diagnostic value of cardiovascular reflex tests is reduced as far as cardiac autonomic neuropathy is concerned. In older patients, the tests are not suitable for the diagnosis of diabetic autonomic neuropathy. More specific methods are required.

Isometric exercise for the evaluation of vasodilatory therapy in severe congestive heart failure

There are few data available about the hemodynamic effects of isometric handgrip in severe congestive heart failure and its role in the evaluation of vasodilatory therapy. Therefore, we studied 20 patients with dilated cardiomyopathy at rest, during isometric handgrip, and during supine bicycle exercise before and after a single 25-mg dose of captopril. During handgrip, heart rate (p less than 0.001); systemic vascular resistance (p less than 0.01); systolic, mean, and diastolic pulmonary artery pressure (p less than 0.01) increased significantly; stroke volume index fell (p less than 0.05); whereas mean arterial pressure showed only a small increase, and cardiac index did not change. In contrast, mean arterial pressure and cardiac index increased during dynamic exercise (p less than 0.001), and peripheral resistance decreased (p less than 001). During both handgrip and bicycle exercise, captopril induced a decrease of arterial pressure (p less than 0.01 and p less than 0.001; respectively), peripheral resistance (p less than 0.001 and p less than 0.01; respectively), and systolic (p less than 0.01 and p less than 0.001, respectively) mean (p less than 0.001), and diastolic pulmonary artery pressure (p less than 0.001). Captopril induced and increase in stroke volume index (p less than 0.01) and cardiac index (p less than 0.001 and p less than 0.01 respectively) during both types of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproducibility of pressor response to handgrip: influence of time intervals, strength and duration of exercise

1. The reproducibility of pressor response to handgrip performed at different time intervals and with different combinations of the product duration x strength of the exercise was evaluated in 14 normotensive subjects recording blood pressure with a noninvasive automatic device. 2. Subjects underwent five consecutive tests (30% of maximal voluntary contraction x 90 s) at 30 min, and 24 h intervals and repeated the test after 12 months. Furthermore, they underwent at 24 h intervals a randomized sequence of handgrip tests whose product strength x duration was combined in order to achieve either a constant or an increasing level of exercise. 3. Blood pressure response to exercise performed at 30 min intervals was much less reproducible than that induced by handgrip performed at time intervals greater than or equal to 24 h. 4. Increasing gradually the product strength x duration of the handgrip test there was a proportional blood pressure increase, whereas when the product was maintained constant diastolic blood pressure increase was also constant and reproducible within each subject. 5. This study shows that it is possible to obtain reproducible diastolic blood pressure responses to handgrip test measuring blood pressure with a non-invasive automatic device when the tests are performed at a time interval of at least 24 h. The choice of the strength and of the duration of the exercise is very important for the reproducibility of the test.

The association between cardiovascular response tasks and future blood pressure levels in children: Bogalusa Heart Study

Children were selected from a total community survey and categorized into three blood pressure (BP) groups (low less than 10 percentile, midrange 10 to 90 percentile, high greater than 90 percentile) based on resting diastolic pressure (DBP). To examine the relationship of cardiovascular reactivity with BP levels 4 years later, three cardiovascular response tasks (orthostatic, handgrip, and cold pressor) were administered. Partial correlations, adjusted for initial resting BP, showed that peak BP responses to the three tasks were related to future resting systolic and diastolic BP. Further analyses showed that DBP reactivity was related to future BP tracking in children with high DBP levels. In the high DBP group, while resting DBP levels did not differ for trackers vs nontrackers, peak DBP responses to each of the three tasks did (orthostatic, p less than 0.001; handgrip, p less than 0.05; cold pressor, p less than 0.01). The combination of resting and peak BP levels may provide more powerful predictions of future BP levels in children.

Temporal stability of psychophysiological responding: a comparative analysis of mental and physical stressors

Although extensive research has been conducted on psychophysiological reactivity, there is a paucity of data concerning the temporal stability of such procedures. Test-retest reliability of experimental stressors from both mental and physical modalities were assessed using a wide range of psychophysiological measures. Absolute baseline and test values demonstrated adequate test-retest reliability for skin temperature, skin resistance, vasomotor response, heart rate, systolic and diastolic blood pressure, while forearm EMG had low reliability. Difference scores, which represent change from baseline to test conditions, did not have adequate reliability. These data represent a necessary step towards standardization of psychophysiological assessment techniques and thus may guide further use of more reliable methods.

Nonpharmacological approaches to the control of high blood pressure. Final report of the Subcommittee on Nonpharmacological Therapy of the 1984 Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure

This report reviews a variety of nonpharmacological approaches used to control arterial blood pressure. Of all the modalities considered, only three had sufficient scientific support to warrant recommendation for inclusion in hypertension treatment programs. Each of these three modalities--weight control, alcohol restriction, and sodium restriction--was found to be capable not only of independently controlling blood pressure (particularly in patients with mild hypertension) but also of reducing the number and dosage of prescribed pharmacological agents, should their prescription be indicated. Weight reduction was found to reduce the risk from elevated arterial pressure as well as overall cardiovascular morbidity and mortality. However, because the rate of recidivism was exceedingly high in these studies, close and continuous patient follow-up is considered necessary. Excessive alcohol intake is associated in many studies with proportionally higher arterial pressures and an increased prevalence of hypertension. Therefore, the recommendation of moderation in alcohol consumption to less than 2 oz of ethanol daily for patients with hypertension is supported. Restriction of dietary sodium to less than 2 g/day was the only other nonpharmacological approach with sufficient support to be recommended as a treatment for hypertension. Although long-term studies are sorely lacking, sodium restriction has been shown to be manageable and safe and probably will benefit those hypertensive patients who are sodium-sensitive.

Effect of parasympathetic impairment on the haemodynamic response to handgrip in Chagas's heart disease

Haemodynamic responses to sustained isometric exercise (handgrip at 30% of maximum voluntary capacity) were studied in 10 patients with Chagas's cardiopathy without previous or current heart failure. Five of the patients (group 1) had profound impairment of parasympathetic control of heart rate. They had no tachycardia in response to intravenous administration of atropine and no bradycardia during phase IV of the Valsalva manoeuvre. The other five (group 2) showed normal vagal regulation of heart rate, as judged by chronotropic responses to these tests. The heart rate change (mean (SD] elicited by the handgrip test was significantly lower in group 1 (from 93.0 (14.1) to 95.0 (16.7) beats/min) than in group 2 (from 78.2 (15.8) to 92.8 (18.1) beats/min). Pressor responses to handgrip were of similar magnitude (from 91.6 (7.8) to 109.0 (8.0) mm Hg in group 1 and from 88.6 (11.9) to 106.8 (20.9) mm Hg in group 2). In both groups no significant change in stroke index was detected during handgrip. Cardiac index increased during handgrip from 4.0 (1.2) to 4.8 (1.3) 1/min/m2 in group 2, but there was no significant change in group 1 (from 4.9 (0.7) to 4.8 (1.1) 1/min/m2). Changes in calculated systemic vascular resistance were significantly higher in group 1 (from 934 (175) to 1176 (383) dyn s cm-5) than in group 2 (from 1109 (404) to 1112 (424). This study shows that parasympathetic impairment adversely influences the haemodynamic pattern of response to isometric exercise in patients with Chagas's heart disease. In such conditions, the pressor response to handgrip is predominantly mediated by an increase in systemic vascular resistance rather than an increase in cardiac output.

Isometric exercise in patients with chronic advanced heart failure: hemodynamic and neurohumoral evaluation

We evaluated the hemodynamic effects of isometric exercise in 53 patients with congestive heart failure (CHF) and compared them with those found in 10 normal subjects. In both groups, isometric exercise increased heart rate and blood pressure. Systemic resistance increased in patients with CHF (1862 +/- 520 vs 2126 +/- 642 dyne-sec-cm-5; p less than .001) but not in normal subjects (1359 +/- 268 vs 1380 +/- 252 dyne-sec-cm-5). Cardiac index and stroke volume index increased mildly but not significantly in the normal subjects (2.8 +/- 0.5 vs 3.1 +/- 0.7 liters/min/m2 and 46 +/- 8 vs 47 +/- 7 ml/m2) and showed a significant fall in the patients with CHF (2.1 +/- 0.6 to 1.9 +/- 0.6 liters/min/m2, p less than .01 and 23 +/- 7 vs 20 +/- 7 ml/m2, p less than .01). Mean pulmonary arterial wedge pressure increased in patients with CHF from 26 +/- 7 to 30 +/- 8 mm Hg (p less than .001). Although no significant change was found in mean value for stroke work index (21 +/- 9 vs 20 +/- 9 g-m/m2), the individual changes were variable, with marked decrease (greater than 15%) in 17 of the patients. This hemodynamic deterioration could not be predicted from resting hemodynamics, left ventricular ejection fraction, or functional classification. Isometric exercise resulted in no significant change in circulatory catecholamine levels or plasma renin concentration in our 10 normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardioselective and nonselective beta-adrenoceptor blocking drugs in hypertension: a comparison of their effect on blood pressure during mental and physical activity

The ability of cardioselective and nonselective beta-adrenoceptor blocking drugs, with and without partial agonist activity, to control increases in blood pressure associated with mental and physical activity was compared in 35 subjects with hypertension. Direct measurements of blood pressure and radioenzymatic determinations of plasma norepinephrine were obtained before, during and after four activities, and were repeated after random allocation to treatment with atenolol, metoprolol, pindolol or propranolol. Cardioselective and nonselective drugs modestly reduced the pressor response to reaction time testing, but not to mental arithmetic or isometric exercise. The increase in systolic blood pressure during bicycling was attenuated significantly by the cardioselective drugs atenolol (by 23 mm Hg, or 38%) and metoprolol (21 mm Hg, or 41%), but not by the nonselective agents pindolol (with partial agonist activity) (13 mm Hg, or 20%) and propranolol (10 mm Hg, or 17%) (p less than 0.02 cardioselective versus nonselective; p = NS pindolol versus propranolol). Only bicycle exercise increased plasma norepinephrine concentrations (by 80%). These results suggest that beta-adrenoceptor blocking drugs will not attenuate increases in blood pressure during mental or physical activities unless intense sympathoadrenal activation also occurs. Marked elevations in circulating epinephrine, with or without norepinephrine, and peripheral beta 2-blockade appear necessary for alpha-mediated vasoconstriction to predominate and for the contrasting effects of cardioselective and nonselective drugs to be appreciated.

Exercise and hypertension

Hypertension is a major risk factor for atherosclerosis. In this article the authors review the use of physical activity as therapy for elevated blood pressure and explore the hemodynamic effects of exercise among patients with treated and untreated hypertension. Recommendations concerning the use of exercise in the management of hypertension are outlined.

Use of non-drug therapy in treating hypertension

The high degree of risk for cardiovascular disease and the failure of medication to provide adequate protection are the chief considerations in the use of nondrug therapy of hypertension. We shall examine the effects of weight reduction, sodium restriction, exercise, and other such alternatives to blood pressure-lowering medication. If nondrug therapies can lower blood pressure, they will remove the need for drug therapy in some patients and minimize the amount of drugs needed for others.

Magnitude and mechanisms of the antihypertensive action of labetalol, including ambulatory assessment

The blood pressure (BP) effect and modes of action of a twice daily regimen of labetalol (mean 450 mg/day) were assessed in ten mild to moderate hypertensives using continuous ambulatory BP monitoring. The reflex control of BP during physiological interventions was examined just prior to the next dose of medication to estimate the residual alpha- and beta-adrenoceptor blockade. Global 24 h BP was reduced by 15/9 mm Hg, and home pressures by 13/11 mm Hg. The predominant antihypertensive effect was noted during the waking hours. During dynamic exercise significant inhibition of the heart rate and blood pressure rise occurred. Coupled with a reduction of the post-release BP 'overshoot' in Valsalva's manoeuvre, the response resembles that seen with beta-adrenoceptor blockade. A small alpha-adrenoceptor blocking action was evident in one patient's response to the Valsalva manoeuvre.

Sympathetic contribution to the cardiac response to stress in hypertension

Studies of cardiac performance in hypertension have often been restricted to cardiac output determinations, although the latter alone are inadequate for that purpose. To define the range of cardiac performance in hypertension, the response of left ventricular filling pressure to increased workload (static exercise) was determined in 39 subjects--eight normotensive (NT) volunteers, seven patients with borderline hypertension (BLH), and 24 essential hypertensives (EH), of age-matched groups. A rise of mean pulmonary wedge pressure (PWP) by 5 mm Hg or more during maximum handgrip (HG) was considered "abnormal" for a workload (SBP x HR x 10(-3)) increase of greater than or equal to 25%. All NT subjects and all patients with BLH as well as 16 of the 24 EH (EH-I) showed normal cardiac performance by this definition. In contrast, PWP increased greater than or equal to 5 mm Hg during HG in eight patients with EH (EH-II). The calculated increase in cardiac workload was not significantly different among the four groups (+5, 5.8, 5.4 and 5.5 respectively). Beta blockade (propranolol, 10 mg i.v.) slowed heart rate in all subjects and reduced SBP x HR product in all groups both at rest and during HG. Responses of PWP to HG were widely divergent in the different patients. However, as a group those patients with "impaired cardiac performance" before propranolol (EH-II) had a greater reduction in performance following propranolol than EH-I or NT. This study suggests that adrenergic support of cardiac performance might be important in some hypertensive patients with no evidence of heart failure.

The effect of captopril and propranolol on the responses to posture and isometric exercise in patients with essential hypertension

The effects of captopril and propranolol on blood pressure, heart rate and plasma noradrenaline, renin and aldosterone, and on the responses to changes in posture and to isometric exercise were measured in patients with essential hypertension. During placebo administration blood pressure, heart rate and plasma noradrenaline rose on standing and during isometric exercise. The rise in diastolic blood pressure during isometric exercise correlated significantly with the rise in plasma noradrenaline. During captopril treatment blood pressure was significantly lower than during placebo administration when the patients were lying, standing or sitting, but the reduction during isometric exercise was not significant. Plasma renin increased, but heart rate, plasma noradrenaline and plasma aldosterone remained unchanged. The acute changes in blood pressure, heart rate and plasma noradrenaline produced by standing and isometric exercise during captopril treatment were similar to those during placebo administration. During propranolol treatment diastolic blood pressure was significantly lower than during placebo administration when the patients were lying, standing or sitting and during isometric exercise. Heart rate also fell. Plasma noradrenaline during standing, sitting and isometric exercise was significantly greater than during placebo administration. The changes in plasma noradrenaline measured during propranolol treatment with the patients supine were negatively correlated with noradrenaline values obtained during placebo administration: plasma noradrenaline fell in patients with higher, and increased in those with lower, initial concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-hypertensive action of labetalol: a detailed profile

Continuous, ambulatory blood pressure (BP) and self measured home recordings were used to study the response of ten mild to moderate hypertensives taking a twice daily labetalol dosage. Testing of cardiovascular reflexes was carried out 12 hours after a dose of drug. The mean 24 hour BP was reduced from 145/80 +/- 14/7 (SD) mmHg to 130/71 +/- 11/6 (p less than 0.001) and home BP from 147/96 +/- 15/9 to 134/84 +/- 10/9 (p less than 0.01). The predominant effect of labetalol was evident during the waking hours. A residual 9.5% BP reduction was seen 12 hours after a dose compared to an 11% lowering effect over the entire 24 hours (NS). No symptomatic hypotensive episodes were noted. Significant inhibition of heart rate and BP rise during dynamic exercise (p less than 0.01) and reduction of post-release BP "overshoot" (p less than 0.01) in Valsalva's manoeuvre indicated a beta adrenoceptor blocking effect. There was however a reduction in the rate of rise of BP during static handgrip (p less than 0.01) indicating a small alpha adrenoceptor blocking component. This study has demonstrated the efficacy of a twice daily regimen of labetalol in continuously lowering BP. The mode of action of the drug during exercise (static and dynamic) and Valsalva's manoeuvre would indicate a predominant beta adrenoceptor blocking action.

A study of nadolol to determine its effect on ambulatory blood pressure over 24 hours, and during exercise testing

1 The effect of once daily nadolol therapy in sixteen ambulant patients with essential hypertension has been closely assessed during exercise and over 24 h by continuous intra-arterial recording. 2 The drug was well tolerated and showed similar efficacy to other beta-adrenoceptor blocking agents. Whilst blood pressure reduction was observed throughout the whole day, it was not uniform and lost significance during the morning period when blood pressure levels were highest. 3 This provides further evidence that the antihypertensive action of a beta-adrenoceptor drug over 24 h cannot be predicted from its plasma half-life which, with regard to nadolol, is up to 24 h. 4 An explanation for the loss of blood pressure control during the morning may be that the rapid rise in blood pressure leading to the peak levels at this time may be mediated through alpha- rather than beta-adrenergic receptors at the periphery.

The value of grip test as an index of autonomic function in hypertension

The autonomic sympathetic adjustments to sustained handgrip, upright tilt, and the Valsalva maneuver, were tested in a total of 52 patients, 26 with labile and 26 with fixed essential hypertension. Sustained handgrip (SHG) increased arterial pressure, heart rate (HR), cardiac index (CI), and tension time index (TTI) (p less than 0.01), but had no effect on total peripheral resistance index (TPRI) and left ventricular ejection rate index (LVERI) in either group of patients. The response to upright tilt and the Valsalva maneuver was different in the two groups. Upright tilt in labile hypertensives increased diastolic arterial pressure (DAP), mean arterial pressure (MAP), HR, and TPRI (p less than 0.001), and decreased CI, stroke index (SI), and LVERI (p less than 0.01), and had no effect on systolic arterial pressure (SAP). In fixed hypertensives, it decreased (SAP, MAP, CI, SI, and LVERI (p less than 0.001), increased HR (p less than 0.01), and had no effect on DAP and TPRI. The diastolic pressure overshoot of the Valsalva maneuver was attenuated in fixed hypertensives compared to labile hypertensives (P less than 0.001). Also, when the percent changes from control in diastolic and mean arterial pressure, heart rate, and total peripheral resistance index after sustained handgrip and upright tilt between the two groups of patients were compared, only upright tilt brought out the differences between the two groups. The results of this study indicate that upright tilt and the Valsalva maneuver are better predictors of autonomic function in hypertension than the grip test.

Response of blood pressure and plasma norepinephrine to propranolol, metoprolol and clonidine during isometric and dynamic exercise in hypertensive patients

The effects of metropolol (beta 1-selective), propranolol (nonselective) and clonidine (central alpha-stimulant) on plasma norepinephrine, blood pressure and heart rate were assessed at rest, during isometric work and dynamic exercise in 15 patients with moderate hypertension. Metroprolol resulted in a lower diastolic blood pressure during isometric and dynamic exercise that propranolol, which was paralleled by a lower plasma norepinephrine level during dynamic work; both beta-adrenergic blocking compounds resulted in a lower heart rate in all test situations than that obtained with clonidine; clonidine produced similar control of diastolic blood pressure to that obtained with the beta-adrenergic blocking agents, but did not clearly attenuate the systolic blood pressure response to dynamic exercise. Plasma norepinephrine concentrations tended to be lowest following clonidine, especially during dynamic work. The findings support the hypothesis that the central action of clonidine inhibits peripheral release of norepinephrine, but is insufficient to attenuate cardiac stimulation by physical exercise. The fact that propranolol caused higher plasma norepinephrine concentrations than metoprolol during exercise may explain the difference in the blood pressure responses during exercise.

Failure of anti-hypertensive drugs to control blood pressure rise with isometric exercise in hypertension

Isometric exercise causes a substantial rise in BP in normotensive and untreated hypertensives. The authors studied the isometric hand-grip test in 5 groups of treated hypertensives, namely beta-blockers, beta-blockers + diuretics, beta-blockers + diuretics + vasodilators, alpha-methyldopa alone and labetalol. All groups showed a substantial rise in both systolic and diastolic BP, and the increments in BP differed little from that in normotensives. Some patients, despite multiple therapy, achieved increments of up to 60 mmHg from rest. Treated hypertensives with cardiac and cerebro-vascular disease are at risk performance isometric exercise.

Prolonged isometric exercise. Part 1: Effect on circulation and on renal excretion of sodium and potassium in mild essential hypertension

The effect of stress, in the form of prolonged isometric exercise, on the circulation and on the renal excretion of sodium and potassium was studied in 18 patients with mild essential hypertension. Thirteen men and five women, aged 20 to 50 years with basal diastolic blood pressure (BP) between 90 and 110 mm Hg were matched by age, sex, and race with 18 controls who had basal diastolic BPs less than 85 mm Hg. After the subjects rested for 90 minutes, basal measurements of pulse rate, BP, and rates of sodium and potassium excretion were made. The subjects then underwent a 1-hour period of isometric exercise involving all four limbs in rotation, followed by 5 hours of rest during which the measurements were repeated at half-hourly intervals for the first 2 hours and at hourly intervals for the last 3 hours. On another day, the subjects were again studied after 1 hour of resting instead of exercise. Responses of each subject were then expressed as ratios of changes from the basal values observed on the exercise and rest days. Changes in systolic and diastolic BP and hart rate were not significantly different in the hypertensive and control groups. In hypertensive subjects, the rate of sodium and potassium excretion was decreased after isometric exercise compared with the rest day, whereas in normal subjects this response was reversed. For the first 3 hours after exercise, the cation excretion rate of the hypertensive group was significantly less than that of the control group. These results indicate that isometric exercise in mild hypertension induces prolonged renal retention of both sodium and potassium.

Hemodynamic correlates of autonomic reflexes in patients with labile and fixed hypertension

the autonomic sympathetic reflexes to sustained handgrip, upright tilt and the Valsalva maneuver, were tested in 26 patients with labile and 26 with fixed essential hypertension. Sustained handgrip increased systolic (SAP), diastolic (DAP) and mean arterial (MAP) pressure, heart rate (HR), cardiac index (CI), tension time index (TTI) (p less than .01), and had no effect on total peripheral resistance index (TPRI) and left ventricular ejection rate index (LVERI) in both groups of patients. However, the response to upright tilt and the Valsalva maneuver was different in the two groups. Upright tilt in labile hypertensives increased DAP, MAP, HR, and TPRI (p less than .001); decreased CI, stroke index (SI) and LVERI (p less than .01) and had no effect on SAP. In fixed hypertensives, it decreased SAP, MAP, CI, SI and LVERI (p less than .001); increased HR (p less than .01) and had no effect on DAP, and TPRI. The diastolic pressure overshoot of the Valsalva maneuver was attenuated in fixed hypertensives compared to labile (p less then .001). Additionally, when the percent changes from control in DAP, MAP, HR and TPRI to sustained handgrip and upright tilt between the two groups were compared, only differences to upright tilt between the two groups were observed. The results of this investigation suggest that upright tilt and the Valsalva maneuver might serve as better predictors of autonomic reflexes in hypertensive patients than the grip test.

Hexamethonium modification of cardiovascular adjustments during combined static-dynamic arm exercise in monkeys

In weight lifting and rowing, essentially the same groups of muscles contract in isometric (static) and isotonic (dynamic) fashion. To approximate the combined static-dynamic arm movements involved in rowing or lifting weights, four rhesus monkeys were trained to pull a T-bar and thereby avoid tail shock. Each animal received 8 daily test sessions in which loads (0.4, 0.8, 1.2, 1.6 kg), total pulls (3, 6, 9, 12 at a constant pull frequency, 0.5 Hz) and alternate sessions of pulling after injection of hexamethonium chloride (7 mg/kg) or saline were factorially combined. Our data indicate that heart rate in this model is primarily influenced by the duration of the dynamic exercise component (number of pulls) in this specific exercise task whereas both dynamic and static components affect systolic and diastolic blood pressure. After ganglionic blockade, heart rate and diastolic pressure do not change appreciably during T-bar pulling while the rise in systolic pressure is attenuated and varies primarily as a function of the static exercise component. The clinical implications of these experiments are discussed.

Racial contrasts in cardiovascular response tests for children from a total community

Cardiovascular risk factors in childhood were assessed by re-examining a random sample of 278 children stratified by diastolic blood pressure (BP), obtained from 3524 children aged 7-15 years in an entire geographic biracial community (Bogalusa). Re-examination included plasma renin and serum electrolytes, 24-hour urine electrolytes, heart rates, and BP at rest and in response to standardized physical stresses (orthostatic, isometric handgrip, and cold pressor tests). The BP responses in these tests were not increased in the high BP strata, which argues against a prevailing labile phase in early essential hypertension. Black children tended toward larger BP responses than whites. In black boys of the high BP stratum (n = 25), systolic supine or stressed BP were higher than for other race-sex groups; these pressures were associated negatively with plasma renin activity, which was low. White children in the high BP strata had increased heart rates, possibly indicating hyperkinetic circulation. These findings indicate that multiple mechanisms operate to contol BP at different intensities for black and white children.

Changes in plasma noradrenaline and adrenaline during isometric exercise

1. Plasma noradrenaline and adrenaline were measured radioenzymatically in twelve hypertensive and four normotensive subjects before and during handgrip. In the resting arm (n=11), plasma noradrenaline increased by 17% (P<0.01) and plasma adrenaline by 27% (P<0.001). In the exercising arm, plasma adrenaline increased by 97% (P<0.005) but the mean increase of noradrenaline of 10% was not significant (P>0.1). 2. The noradrenaline response suggests a small and variable sympathetic adrenergic response; the significant difference (P<0.05) in adrenaline responses between resting and exercising arms may reflect local variation in tissue clearance.

Effects of labetalol and propranolol on blood pressure at rest and during isometric and dynamic exercise

The influence of intravenous labetalol and propranolol on the blood pressure response to isometric and dynamic exercise was examined in a double blind study in eight, young, normotensive volunteers. Effects were recorded after propranolol 7.5, 15 and 30 mg i. v., and after labetalol 30, 60 and 120 mg i. v. In control experiments saline was administered. Mean blood pressure rose with successive handgrip tests following saline and propranolol, but not after labetalol, and the difference was significant. The total dose of each drug produced the same reduction in heart rate during sub-maximal bicycle exercise. The exercise-induced systolic blood pressure response did not differ between the drugs.

The effects of alpha- and beta-adrenergic receptor blockers on the pressure responses to isometric exercise in hypertensive patients

1. The cardiovascular responses to handgrip exercise have been studied in ten patients with uncomplicated essential hypertension in a randomized crossover study of propranolol and prazosin. 2. Isometric handgrip exercise was performed with a calibrated strain gauge dynamometer at 30% of maximum voluntary contraction for 3 min. 3. Blood pressure and heart rate were measured in the supine position at rest and in the last 10 s of the exercise period. 4. These exercise studies were undertaken at the end of a run-in period and at the end of 1 month's optimal therapy with the two drugs. 5. The active treatment periods were separated by a 2 weeks placebo washout period. 6. Both drugs lowered the supine and standing systolic and diastolic pressures and there was no difference between these drugs in their effect on these variables. 7. Propranolol lowered the resting heart rate and neither drug suppressed the pressor response to isometric exercise. 8. The degree of pressure rise was similar with both drugs but propranolol suppressed isometric exercise-induced tachycardia.

Plasma noradrenaline response to sustained handgrip in patients with essential hypertension

The responses of plasma noradrenaline, arterial blood pressure, and heart rate to sustained handgrip at 30% maximal voluntary contraction were studied in untreated patients with essential hypertension and in healthy subjects of comparable age. There were no significant differences between these two groups in the intensity and duration of handgrip. Increases in heart rate and blood pressure induced by the effort were similar in hypertensive patients and normotensive control subjects, whereas the absolute levels of blood pressure were considerably higher in the patients. In the first 1-2 min of exercise the increases in plasma noradrenaline concentration were similar in both groups. Subsequently, plasma noradrenaline concentration tended to plateau in hypertensive patients while in control subjects it continued to increase. The elevation of plasma noradrenaline in the last minute of effort was, therefore, significantly smaller in hypertensive patients than in the control group.

Effect of labetalol in hypertension during exercise and postural changes

1 Fourteen hypertensive patients were studied by intra-arterial BP monitoring to quantify the effects of standardized physiological stresses: Valsalva manoeuvre, isometric, treadmill and bicycle exercise, and 60 degree tilting before and after labetalol treatment. 2 The dose of labetalol ranged from 100--600 mg three times daily and the response was judged on outpatient clinic recordings. 3 The drug produced a sustained reduction of BP and heart rate responses during dynamic exercise and the Valsalva manoeuvre, but the degree of change from the lowered baseline were not changed by labetalol. The fall in BP on cessation of exercise was decreased rather than increased. 4 The response to controlled isometric muscle contraction was affected in a similar fashion. 5 Tilting produced a fall in BP after treatment, and this was most marked in those patients on the highest doses. However, compensatory increases in diastolic BP were observed.

Comparison of intra-arterial and indirect blood pressures at rest and during isometric exercise in hypertensive patients before and after metoprolol

1. Blood pressure was measured both directly and indirectly in seven hypertensive patients before and after a single oral dose of 100 mg metoprolol, at rest and during sustained handgrip. 2. Intra-arterially measured systolic and diastolic blood pressure increased linearly with time during sustained handgrip at 50% of maximal voluntary contraction. This linearity persisted for 60 s or more in most cases. Heart rate increased linearly for the first 30 s. 3. Indirectly measured blood pressure using an observer bias minimizing Auto-Manometer, under-read systolic and over-read diastolic pressure both at rest and during handgrip. 4. By exact timing of recorded values during handgrip and linear extrapolation (or interpolation) from base-line readings, mean values at 30 and 60 s of handgrip were calculated. The relationship between direct and indirect values remained the same at base-line and 30 s of handgrip. At 60 s of handgrip, this was true only for diastolic pressure. For systolic pressure, indirect and direct values almost coincided. 5. After metoprolol, directly recorded pressure fell slightly (7--12 mm Hg, 0.02 less than P less than 0.10), both at rest and during handgrip, and heart rate fell by 15--18 beats/min (P less than 0.01). The systolic blood pressure and heart rate effect of metoprolol at 1 min handgrip correlated with peak plasma drug levels. Indirectly measured blood pressure did not change significantly. 6. The rate of rise in heart rate and blood pressure from base-line to 60 s handgrip was not significantly influenced by metoprolol.

Pressor response to saralasin (1-sar-8-ala-angiotensin II) bolus injection in hypertensive patients

A 10 mg bolus of the angiotensin blocker saralasin was injected 113 times in 68 subjects with essential or renovascular hypertension. Ninety percent of injections caused a transient increase in blood pressure, which correlated with plasma renin activity (PRA) (r = -0.54); Mean increase at 2 minutes was 21/13.4 mm Hg (P less than 0.001) and was independent of pre-injection control blood pressure, with a rapid decrease to or below control values thereafter. Thirty-seven subjects were studied on successive days before and after furosemide-induced sodium depletion (152 +/- 26 mEq [SE] sodium loss). In the low renin group, sodium depletion did not change PRA or the magnitude of the pressor response to saralasin, but significantly decreased control MAP by 13 mm Hg (P less than 0.01). In normal and high renin patients, MAP was unchanged after diuresis, but PRA increased significantly and the pressor response was attenuated. The net effect of sodium depletion was to reduce the pressor response to saralasin in all renin subgroups by 9 to 12 mm Hg. Saralasin bolus injection, unlike infusion, saturates available vascular receptors only briefly, eliminating prolonged pressor responses.

Hemodynamic effects of isometric exercise in normotensive and hypertensive subjects

Isometric exercise increases arterial pressure and heart rate in normotensive individuals and also in patients with labile and fixed essential hypertension. The hypertensinogenic effect of isometric exercise is mediated through an increase in cardiac output because the peripheral vascular resistance is usually not affected. The cardioaccelerating effects of isometric exercise are mediated through an initial vagal withdrawal and a later stimulation of the sympathetic system. However hypertensive patients with defective sympathetic adjustments are not immune to the hypertensinogenic and cardioaccelerating effects of isometric exercise. Since isometric exercises are performed several times during daily activities, they may result in dangerous elevations in arterial pressure in patients with already increased arterial pressure, and this may eventually lead to cerebrovascular accidents and/or cardiac decompensation. It is therefore recommended that patients with elevated arterial pressure, or persons prone to hypertension, should refrain from such activities.

The effects of exercise on the amplitude of the first heart sound in normal subjects

The cardiovascular responses to isometric and dynamic exercise have been studied in six normal subjects, before and after intravenous propranolol, using the amplitude of the first heart sound (S1), measured from an ultra-low frequency phonocardiogram, as an index of left ventricular mechanical performance. Dynamic exercise caused significant increases in heart rate and S1 amplitude which were largely inhibited by beta-adrenergic blockade. Isometric exercise also produced increases in heart rate and blood pressure, but a decrease in S1 amplitude. Propranolol had no significant effect on the cardiovascular response to isometric exercise. These results confirm previous suggestions that, in contrast to dynamic exercise, the normal cardiovascular responses to isometric exercise are relatively independent of the beta-adrenergic nervous system. Possible reasons why the improvement in left ventricular performance, which has previously been shown to occur during isometric handgrip, was not reflected in the phonocardiogram, are also discussed.

Indirect blood pressure and heart rate measured quickly without observer bias using a semi-automatic machine (auto-manometer)--response to isometric exercise in normal healthy males and its modification by beta-adrenoceptor blockade

1 In a double-blind crossover study, six volunteers performed sustained handgrip at 50% of maximal voluntary contraction before and 90 min following oral administration of 0.25 and 100 mg metoprolol tartrate, a beta1 selective adrenoceptor blocking agent. Blood pressure and heart rate were measured with the Auto-Manometer, an electronic semi-automatic device based on the principles of the London School of Hygiene and Tropical Medicine sphygmomanometer. It eliminates observer and digital bias completely, and also records heart rate at the same time as blood pressure is recorded. 2 Resting heart rate fell 15% after 25 mg, 21% after 100 mg and was unchanged after placebo. Systolic blood pressure fell 6% on both doses and was unchanged on placebo. Diastolic pressure did not change with any of the doses. 3 At 1 min of handgrip, heart rate was significantly lower after 25 and 100 mg than before drug or after placebo. There was no difference between the blood pressure levels attained before or after any of the dose levels. The rise of heart rate tended to be somewhat dampened after 100 mg only. The rise in blood pressure was unchanged after any dose compared with before.

Exertional hypotension due to postganglionic sympathetic blocking drugs

Debrisoquine, guanethidine and bethanidine may produce troublesome hypotensive symtoms related to exertion. Thirteen patients with such symptoms were exercised on a treadmill and the response of blood pressure and heart rate was compared to that of thirty patients without these symptoms, who were exercised to the same extent. There was a slight drop of systolic and diastolic pressures on standing in both groups, but after exertion there was a significantly greater drop of systolic pressure in the group with symptoms than in the asymptomatic group. The diastolic pressure after exertion was significantly lower in the group with symptoms. It was impossible to predict from the standing blood pressure levels at rest which patients would develop hypotensive symptoms after exertion. All three drugs had a similar negative chronotropic effect at rest and on exercise. It is suggested that patients are exercised during control of hypertension in order to identify those prone to exertional hypotension. Patients with such hypotension should be exercised on each attendance before the blood pressure is measured. Treatment other than postganglionic sympathetic blocking drugs should be employed whenever possible in patients with milder hypertension.

British pilot study of exercise therapy. II. Patients with cardiovascular disease

Two groups of middle-aged men, one with and one without overt cardiovascular disease, were studied while they were taking part in a specially designed course of exercise therapy in a gymnasium. The "patients" group had at least two months pre-treatment to allow physical recovery and mental re-education before their initial very small test dose of exercise. Using short periods of progressive, mainly weight-loaded, isotonic exercises carefully regulated by control of pulse rate and avoidance of symptoms of over-exertion, both groups showed large increases in effort capacity and reductions in resting pulse rate, blood pressure and plasma lipid levels within two months. The safety of this particular form of exercise was shown in this high-risk population by the low drop-out rate and the absence of cardiovascular accidents in the gymnasium over a ten year period. It is suggested that, given suitable training of the staff and using the safeguards described, the presence of doctors and a cardiac resuscitation team is unnecessary in a gymnasium specializing in cardiac rehabilitation. This makes it possible for rehabilitation and physiotherapy departments throughout the country to carry out this effective and positive form of exercise therapy.

Incidence of arrhythmias induced by isometric and dynamic exercise

The incidence of arrhythmias during isometric sustained handgrip exercise and during dynamic graded bicycle exercise was compared in a group of 45 patients with various forms of heart disease on no antiarrhythmic therapy. Atrial arrhythmias were equally common during handgrip and bicycle exercise but ventricular arrhythmias were more frequent during handgrip exercise. Of the 45 patients, 38 per cent developed ventricular arrhythmias during isometric exercise, with ventricular tachycardia occurring in 15 per cent. During dynamic exercise 22 per cent of the 45 patients developed ventricular arrhythmias, with ventricular tachycardia occurring in 2 per cent. Patients with coronary artery disease and/or depressed left ventricular function developed twice the incidence of ventricular arrhythmias with isometric than with dynamic exercise. Thus, isometric exercise testing is of more value than dynamic exercise testing in unmasking latent ventricular arrhythmias in patients with heart disease.

Beta adrenergic blockade and diuretic therapy in benign essential hypertension: A dynamic assessment

Beta adrenergic receptor antagonists (beta blockers) differ greatly in their cardioselectivity and intrinsic sympathomimetic activity, and these differences may have important therapeutic consequences. We have therefore studied the effect on blood pressure, heart rate and plasma renin activity of the beta blocking drug oxprenolol (Trasicor) which has considerable intrinsic sympathomimetic activity, both alone and in combination with the benzothiadiazine cyclopenthiazide. Eleven patients with mild to moderate benign essential hypertension were randomly allocated to one of two treatment groups. Oxprenolol was given as the first drug to Group 1, and cyclopenthiazide as the first drug to Group 2. The patients were assessed before the start of treatment, after 2 to 3 weeks of treatment with one drug and after a further 2 to 3 weeks of treatment with both drugs. Heart rate, blood pressure and plasma renin activity were measured with the patients recumbent and after a standardized tilt to 85 degrees to provide a reflection of day to day cardiovascular stress. Oxprenolol reduced arterial blood pressure without inducing significant bradycardia. The addition of cyclopenthiazide had little further effect. Oxprenolol alone suppressed plasma renin activity both at rest and during tilt and also abolished the increase in plasma renin activity after administration of cyclopenthiazide. The combination of (1) moderate reduction of blood pressure. (2) inhibition of the otherwise inevitable increase in plasma renin activity with the use of a diuretic drug, and (3) only moderate inhibition of overall sympathetic activity indicates that it is possible to achieve physiologic balance with the appropriate beta blocking drug.

Weight carrying after myocardial infarction

The blood-pressure responses to carrying a 15 kg. weight in a shoppong basket, and in a rucksack on the back, were compared in 13 ambulant male patients who were convalescing from an uncomplicated myocardial infarction. In 8 of the patients a sustained-handgrip test was also performed. Carrying the weight in the hand produced a distinct increase in blood-pressure, which did not occur when the weight was carried on the back. There was also a significant increase in blood-pressure during sustained handgrip. In view of the lack of symptoms with these circulatory changes, it is concluded that more specific advice about the possible dangers of sustained static exercise should be given to patients recovering from myocardial infarction.