Systemic and renal hemodynamics in oliguric hepatic failure: effect of volume expansion.

Systemic and renal hemodynamics were studied by indicator dilution techniques before and after infusion of 500 ml of dextran 40 in 21 patients with renal failure developing in the course of decompensated cirrhosis. Cardiac index was directly correlated with total blood volumes. Renal blood flow was low and renal vascular resistance elevated in 13 of 15 patients. Renal vascular resistance was directly related to total systemic nonrenal vascular resistance. Two patients with the highest cardiac outputs in the group were oliguric with high renal blood flow. Plasma volume expansion increased cardiac output in 19 of 21 patients and increased renal blood flow in 12 of 14. The patients were divided into two groups on the basis of control cardiac index. Those with lower cardiac index had lower blood volumes and responded to dextran with a 73% increase in cardiac output, a 148% increase in renal blood flow, and a rise in renal fraction. Those with high control cardiac index had significantly higher blood volumes and responded to dextran with only a small average rise in cardiac output and renal blood flow. Systolic arterial pressure was less than 100 mm Hg in 12 patients. When compared to the normotensive subjects, this hypotension was characterized by a lower vascular resistance, a tendency for a lesser rise in renal blood flow after volume expansion, and a more rapid demise. The prompt circulatory improvement after volume expansion in many of these patients indicates that functional plasma volume depletion may be an important factor in the renal vasoconstriction of oliguric hepatic failure. In an attempt to sustain volume expansion, reinfusion of ascitic fluid was accomplished in four patients. Normal renal blood flow was maintained during reinfusion and a diuresis always occurred, but the response usually was not maintained after the infusion was terminated.

Mechanism of pulsus paradoxus in clinical shock.

An inspiratory fall in systolic arterial pressure of more than 10 mm Hg (pulsus paradoxus) was noted in 30 of 61 patients with shock. Inspiratory right atrial pressures and total blood volumes were significantly lower in patients with pulsus paradoxus. Rapid infusion of dextran in 22 patients usually was effective in reversing the exaggerated inspiratory fall in systolic pressure. Total peripheral vascular resistance tended to be higher in the patients with pulsus paradoxus and administration of vasoconsrictor drugs often accentuated the respirator pressure variation. Respiratory effects on blood flow in the aorta, pulmonary artery, and venae cavae were studied in anesthetized, closed-chest dogs. In the control state, pulmonary arterial flow increased during inspiration but aortic flow remained nearly constant. After hemorrhage a sharp inspiratory fall in aortic flow was associated with decreased central blood volume and attenuation of the usual inspiratory increase in venae caval and pulmonary arterial flows. The respiratory changes in aortic flow after hemorrhage could be attributed both to depletion of the pulmonary reservoir and to alterations in pulmonary inflow related to changes in systemic venous return. These data indicate that blood volume depletion may precipitate pulsus paradoxus both in the anesthetized dog and in the critically ill patient. The occurrence of pulsus paradoxus may aid in the clinical recognition of the common syndrome of occult hypovolemia in patients with shock in the absence of signs of blood loss.

Studies in clinical shock and hypotension: VI. Relationship between left and right ventricular function.

Left ventricular end diastolic (LVEDP) and mean right atrial (RAP) pressures were recorded simultaneously in 30 patients with shock (14 acute myocardial infarction, 10 acute pulmonary embolism or severe bronchopulmonary disease, and 6 sepsis). Myocardial infarction was characterized by a predominant increase in LVEDP, pulmonary disease by a predominant increase in RAP, and sepsis by a normal relationship between LVEDP and RAP. In all three groups a significant positive correlation was noted between RAP and LVEDP, with the regression line in cor pulmonale deviated significantly toward the RAP axis and the regression line in myocardial infarction exhibiting a zero RAP intercept at an elevated LVEDP.Low cardiac outputs with elevated LVEDP in myocardial infarction indicated severe left ventricular failure. Low outputs with elevated RAP in cor pulmonale were consistent with right ventricular overload. Although cardiac outputs often were normal in sepsis, low outputs with elevated cardiac filling pressures in some patients were consistent with a hemodynamic or humoral-induced generalized depression of cardiac performance.Vasoconstrictor and inotropic drugs often produced a functional disparity between the two ventricles, with the gradient between LVEDP and RAP increasing, apparently because of an increase in left ventricular work or an inadequacy of left ventricular oxygen delivery. Acute plasma volume expansion with dextran in patients with pulmonary vascular disease resulted in a somewhat more rapid rise in RAP than in LVEDP. In septic and myocardial infarction shock, however, LVEDP and RAP usually rose proportionally, with the absolute rise of LVEDP surpassing that of RAP. Although the absolute level of the central venous pressure thus may not be a reliable indicator of left ventricular function in shock, changes in venous pressure during acute plasma volume expansion should serve as a fairly safe guide to changes in LVEDP.

Prevalence and prognostic significance of silent and symptomatic ischemia after coronary bypass surgery: a report from the Coronary Artery Surgery Study (CASS) randomized population.

The prevalence and prognostic significance of postoperative myocardial ischemia, as detected by exercise testing, were prospectively assessed in 174 patients from the Coronary Artery Surgery Study (CASS) randomized surgical population who had exercise testing before and 6 months after coronary artery bypass graft surgery. Whereas the prevalence of symptomatic ischemia significantly decreased postoperatively (52% vs. 6%, p less than 0.001), the frequency of silent myocardial ischemia did not change (30% vs. 29%). Survival at 12 years after bypass surgery based on the 6-month postoperative exercise test results was significantly better for the 112 patients with no ischemia (80%) than for the 51 patients with silent ischemia (68%) or the 11 patients with symptomatic ischemia (45%). These data show that coronary artery bypass graft surgery diminishes the overall prevalence of symptomatic but not silent ischemia and that both silent and symptomatic ischemia adversely affect the postoperative prognosis of these patients.

Effect of head-out water immersion on cardiorespiratory response to dynamic exercise.

Head-out water immersion is known to produce several cardiopulmonary adjustments at rest due to a cephalad shift in blood volume. The purpose of this study was to determine the effect of head-out water immersion on the cardiorespiratory response to graded dynamic exercise. Nineteen healthy middle-aged men performed upright cycling exercise at 40, 60 and 80% of maximal oxygen consumption on land and in water (31.0 +/- 1.0 degrees C) to the shoulders. Cardiac output (measured by the carbon dioxide rebreathing technique) was significantly greater in water at 40 and 80% maximal oxygen consumption. Stroke volume was significantly elevated at all stages of exercise. Heart rate did not differ significantly at 40 and 60% maximal oxygen consumption but was significantly lower in water at 80% maximal oxygen consumption. Total ventilation did not differ significantly in water and on land at any stage of exercise. The results suggest that the central redistribution of blood volume with head-out water immersion leads to an increase in stroke volume. Because there is not a proportional decrease in heart rate with the elevated stroke volume, cardiac output is regulated at a higher level during upright exercise in water compared with that on land. In conclusion, there are serious limitations of available, prerecorded rhythm data bases for designing and testing of automatic external defibrillators. Performance can be adequately assessed only by extensive clinical tests, which seem mandatory for this new and important type of defibrillator.

Effect of age and coronary artery disease on response to snow shoveling.

OBJECTIVES: The objective of this study was to evaluate the effect of age and coronary artery disease on responses to snow shoveling. BACKGROUND: Little information is available on the hemodynamic and metabolic responses to snow shoveling. METHODS: Sixteen men with asymptomatic coronary artery disease and relatively good functional work capacity, 13 older normal men and 12 younger normal men shoveled snow at a self-paced rate. Oxygen consumption, heart rate and blood pressure were determined. In nine men with coronary artery disease left ventricular ejection fraction was evaluated with an ambulatory radionuclide recorder. RESULTS: Oxygen consumption during snow shoveling differed (p < 0.05) among groups; it was lowest (18.5 +/- 0.8 ml/kg per min) in those with coronary artery disease, intermediate (22.2 +/- 0.9 ml/kg/min) in older normal men and highest (25.6 +/- 1.3 ml/kg/min) in younger normal men. Percent peak treadmill oxygen consumption and heart rate with shoveling in the three groups ranged from 60% to 68% and 75% to 78%, respectively. Left ventricular ejection fraction and frequency of arrhythmias during shoveling were similar to those during treadmill testing. CONCLUSIONS: During snow shoveling 1) the rate of energy expenditure selected varied in relation to each man's peak oxygen consumption; 2) older and younger normal men and asymptomatic men with coronary artery disease paced themselves at similar relative work intensities; 3) the work intensity selected represented hard work but was within commonly recommended criteria for aerobic exercise training; and 4) arrhythmias and left ventricular ejection fraction were similar to those associated with dynamic exercise.

Haemophilus parainfluenzae mitral valve vegetation without hemodynamic abnormality. Demonstration by angiography and serial echocardiography.

The occurrence of Haemophilus parainfluenzae endocarditis on a previously normal mitral valve of a drug addict is described. A large mitral valve vegetation was demonstrated by serial echocardiography and cineangiography. The vegetation did not produce hemodynamic abnormalities preventing detection by physical examination. Multiple septic emboli to various organs, including brain, resulted in death. The role of serial echocardiography and the levophase of right heart cineangiography in detecting mitral valve vegetation in a patient suspected of having infective endocarditis is emphasized.

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.

Cardiac response to combined moderate heat and exercise in men with coronary artery disease.

The effect of moderate heat stress on cardiac performance during sustained moderate physical work was evaluated in men greater than or equal to 6 weeks after a cardiac event. Subjects (n = 10) performed upright leg cycle ergometer exercise at approximately 50% of peak oxygen uptake for up to 60 minutes in warm (30.0 +/- 0.9 degrees C) and thermoneutral (21.5 +/- 0.3 degrees C) environments. Cardiac output (carbon dioxide rebreathing method), left ventricular ejection fraction and relative left ventricular end-diastolic volume (portable nuclear VEST monitor) were periodically determined. In both environments, heart rate increased (p less than 0.05), stroke volume decreased (p less than 0.05), and cardiac output remained unchanged with exercise time. In the warmer environment, heart rate was increased (p less than 0.05) and stroke volume tended to be decreased (p less than 0.08), with no difference in cardiac output. In both environments, left ventricular ejection fraction did not change from minute 6 to 60 of exercise, whereas relative left ventricular end-diastolic volume decreased (p less than 0.05) with exercise time. Arterial blood pressure was unchanged from minute 6 to 60 in the warm environment. Arrhythmias were not altered by exercise time or environment, and no subjects had evidence of myocardial ischemia. The data indicate that although heart rate increased and stroke volume and relative left ventricular end-diastolic volume decreased with exercise time, cardiac output and left ventricular ejection fraction remained unchanged in both thermoneutral and warm environments.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of patients after myocardial infarction to carrying a graded series of weight loads.

Cardiovascular responses to carrying graded weight loads of 20 to 50 pounds were determined in 52 patients after myocardial infarction (MI) (greater than or equal to 2 months). Sixty percent of the patients were stopped before completing the heaviest weight load (50 pounds for 2 minutes) because of an increase in diastolic blood pressure (BP) to 120 mm Hg (end point) or arm fatigue. Compared with symptom-limited graded dynamic exercise, peak systolic and diastolic BP were significantly greater (p less than 0.05 and p less than 0.01, respectively) with weight carrying, while peak heart rate, pressure-rate product, ventilation and oxygen consumption were significantly lower (p less than 0.01). Ischemic responses were less frequent with weight carrying. Patients with severely reduced resting left ventricular ejection fraction (LVEF) (less than 35%) tolerated the weight carrying test as well as patients with normal resting LVEFs (greater than 50%). We conclude that (1) ischemic responses occur less frequently while carrying up to 50 pounds for 2 minutes than with symptom-limited dynamic exercise, (2) a significant number of patients have an increase in diastolic BP greater than or equal to 120 mm Hg while carrying objects that weigh 30 to 50 pounds for 2 minutes, and (3) a poor correlation exists between resting LVEF and tolerance for weight carrying.

Weight carrying versus handgrip exercise testing in men with coronary artery disease.

The clinical merits of handgrip and weight carrying tests were compared in 30 patients with documented coronary artery disease. The static loads in the 2 tests were matched by percentage of maximal static effort and corresponded to 25 and 45% of maximal voluntary handgrip contraction and 25 and 45% of maximal 1-hand lift capacity. Each static load in both tests was continued for less than or equal to 3 minutes. At the 25% maximal effort stage, 93 and 90% of patients were able to complete 3 minutes of handgrip and weight carrying, respectively. Only 13 and 10% were able to complete 3 minutes at the 45% maximal effort stage with handgrip and weight carrying, respectively. Arm fatigue and an increase in diastolic blood pressure greater than 120 mm Hg were the predominant endpoints. Weight carrying resulted in significantly higher (p less than 0.05) heart rate, systolic blood pressure, pressure-rate product, ventilation and oxygen consumption compared to handgrip. Diastolic blood pressure responses did not differ between the tests. None of the patients demonstrated ischemic responses to either handgrip or weight carrying and the incidence of arrhythmias was rare. The diastolic blood pressure response to static effort is equally evaluated by handgrip and weight carrying tests. However, the greater myocardial oxygen demand, reflected by the pressure-rate product, in addition to the greater total body oxygen consumption, imposed by weight carrying, enhances the clinical application of the weight carrying test.

Long-term prognostic value of exercise testing in men and women from the Coronary Artery Surgery Study (CASS) registry.

Many prior studies involving a predominantly male population have demonstrated the importance of exercise test results in determining the outcome of patients with coronary artery disease. The prognostic significance of exercise testing in women is unknown. In our study, a total of 3,086 men and 747 women underwent maximal treadmill exercise testing, coronary angiography, and were prospectively followed for up to 16 years. They were divided into 3 groups (high, intermediate, and low risk) on the basis of exercise testing. Sixteen-year survival based on exercise test groups ranged from 38% to 61% in men and from 44% to 79% in women (p < 0.001). Among men, 12-year survival was enhanced by coronary artery bypass surgery versus medical therapy in the high-risk subgroup (69% vs 55%, respectively, p = 0.0025), but the 2 therapies were similar in the intermediate- and low-risk subgroups. Among women, neither medical nor surgical therapy resulted in improved 12-year survival rates in any of the 3 subgroups. These results suggest that exercise testing is helpful in assessing long-term survival in men and women. However, only exercise testing in men could identify a high-risk subset whose survival was enhanced by coronary artery bypass graft surgery.

Energy expenditure during household tasks in women with coronary artery disease.

The energy expenditure for and heart rate responses to common household tasks were determined in 26 older (mean age 62 +/- 2 years) women with coronary artery disease (CAD). Each activity was performed at a self-determined pace for 6 or 8 minutes. The average oxygen uptake (ml/kg/min) for each task evaluated was 6.5 for washing dishes, 6.8 for ironing, 7.2 for scrubbing pans, 8.6 for unpacking groceries, 9.5 for vacuuming, 9.8 for sweeping, 10.1 for mopping, 12.0 for changing bed linens, and 12.4 for washing the floor (hands and knees). None of the subjects reported angina. Mean relative oxygen uptake (i.e., percentage of peak response with treadmill testing) ranged from 31 +/- 2% for washing dishes to 62 +/- 3% for changing the bed linens and washing the floor. Percentage of peak treadmill heart rate ranged from 62 +/- 2% for washing dishes to 73 +/- 2% for washing the floor. In 4 of the more physically demanding household activities (i.e., vacuuming, mopping, washing the floor, and changing bed linens), the responses of 10 age-matched normal women were evaluated. The absolute and relative demands of the tasks were similar between the CAD and normal groups. Results indicate that the mean energy expenditure rate of common household tasks evaluated in this study range from 2 to 4 METs, suggesting that most women with CAD who are able to achieve > or = 5 METs during a treadmill exercise test without adverse signs or symptoms should be able to resume these activities.

Significance of silent myocardial ischemia during exercise testing in patients with diabetes mellitus: a report from the Coronary Artery Surgery Study (CASS) Registry.

To evaluate the significance of ischemic ST depression without anginal chest pain during exercise testing among patients with diabetes mellitus, the data on 45 such patients from the Coronary Artery Surgery Study registry were analyzed. These patients (group 1, silent ischemia) were compared with 37 diabetic patients with both ischemic ST depression and chest pain (group 2, symptomatic ischemia), with 31 diabetic patients without ischemic ST depression or chest pain (group 3, no ischemia), and with 429 patients without diabetes who had silent ischemia during exercise testing. All patients had documented coronary artery disease (CAD) (greater than 70% diameter narrowing). The 6-year survival among patients with silent ischemia was worse in diabetic than nondiabetic patients (59 vs 82%, respectively, p less than 0.001). By contrast, the 6-year survival among patients without ischemia was similar among diabetic and nondiabetic patients (93 vs 85%, respectively, p = 0.476). Among diabetic patients, survival at 6 years with medical treatment was 59% for group 1, 66% for group 2 and 93% for group 3 (p = 0.008). Survival among subsets of patients with diabetes and silent ischemia (group 1) based on the extent of CAD and left ventricular function ranged from 100 to 32% (p = 0.093). The survival of the 45 patients with diabetes mellitus and silent ischemia (group 1) treated medically was compared with that of 28 patients receiving coronary artery graft bypass surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk of developing an acute myocardial infarction or sudden coronary death in patients with exercise-induced silent myocardial ischemia. A report from the Coronary Artery Surgery Study (CASS) registry.

To evaluate whether patients with silent myocardial ischemia during exercise testing are at increased risk for developing a subsequent acute myocardial infarction or sudden death, the data on 424 such patients with proven coronary artery disease (CAD) from the Coronary Artery Surgery Study (CASS) registry were analyzed. These patients (group 1) were compared with 456 other patients with CAD (group 2) who had both ischemic ST depression and angina pectoris during exercise testing and with 1,019 control patients without CAD. The probability of remaining free of a subsequent acute myocardial infarction or sudden death at 7 years was 80 and 91%, respectively, for group 1, 82 and 93%, respectively, for group 2 (difference not significant, compared with group 1), and 98 and 99%, respectively, for the control patients (p less than 0.001), compared with group 1 or 2). Among patients in group 1, the probability of remaining free of myocardial infarction and sudden death at 7 years was related to the severity of CAD and presence of left ventricular (LV) dysfunction, and ranged from 90% for patients with 1-vessel CAD and preserved LV function to 38% for patients with 3-vessel CAD and abnormal LV function (p less than 0.001). Thus, patients with either silent or symptomatic ischemia during exercise testing have a similar risk of developing an acute myocardial infarction or sudden death--except in the 3-vessel CAD subgroup, where the risk is greater in silent ischemia. The risk of patients with silent myocardial ischemia is based primarily on angiographic variables.

Risk factors in patients undergoing a second aorta-coronary bypass procedure.

A group of 38 patients with a second revascularization procedure was studied for factors which may have contributed to the reappearance of angina after the first operation. Our data indicate that these patients usually have the first operation at an earlier age and had fewer bypasses at that time. In addition, they had inadequate control of the plasma triglyceride and cholesterol levels.

Comparison of adaptations and compliance to exercise training between middle-aged and older men.

OBJECTIVE: To compare the rate and magnitude of physiologic and psychologic adaptations to aerobic training between middle-age and older men, to assess their interest in continued participation (> 6 months) in a supervised high-intensity training program, and to evaluate the safety of high-intensity training for older people. DESIGN: Before-after intervention trial. SETTING: Medical center in a Midwestern metropolitan city. PARTICIPANTS: Thirteen middle-age (35-50 years) and 14 older (60-71 years) normal men. INTERVENTION: Subjects trained on treadmills and leg cycle ergometers for 40 minutes 3 times per week. The intensity was increased to 85% of peak heart rate (HR) within the first 3 weeks of training. MEASUREMENT: Peak oxygen consumption, HR at submaximal work rates, three psychological tests, and election to continue in the supervised program. RESULTS: At 6 months of training, peak oxygen consumption had increased by 12% and 11% in the middle-aged and older groups, respectively, with 86% and 100% of this increase occurring within the first 3 months. Both groups showed comparable decreases in HR at submaximal work rates after 3 months of training with no further significant change from 3 to 6 months. None of the psychologic parameters evaluated changed significantly with 3 or 6 months of training in either group. More of the older (71%) than middle-aged (45%) men elected to continue in the supervised program after 6 months. CONCLUSIONS: The results of this study involving small groups of carefully screened middle-aged and older men suggest that the time course and magnitude of physiologic adaptations to aerobic training are similar between age groups when the training regimen is the same. Neither age group showed alterations in psychologic parameters nor experienced orthopedic injuries with training. The older group showed greater interest in continued participation in a supervised exercise program.

Effect of aerobic training on baroreflex regulation of cardiac and sympathetic function.

To investigate the effect of aerobic exercise training on baroreflex regulation of muscle sympathetic nerve activity (MSNA) and cardiac R-R intervals in a middle-aged to older population, 10 healthy men > 40 yr of age underwent tests of autonomic function before and after 12 wk of high-intensity training. Cardiac and peripheral baroslopes were determined from the R-R interval vs. mean arterial pressure (MAP) and peroneal MSNA vs. diastolic pressure relationships, respectively, during sequential bolus injections of nitroprusside and phenylephrine. Maximal oxygen uptake increased (P < 0.05) 17% with training. Resting R-R interval increased (881 +/- 23 to 956 +/- 38 ms, P < 0.05), MAP decreased (96 +/- 2 to 91 +/- 3 mmHg, P < 0.05), and MSNA was unaltered (23.1 +/- 2.3 to 23.6 +/- 1.9 bursts/min) with training. Before and after training, respectively, cardiac baroslopes determined with decreasing (8.7 +/- 0.9 to 9.9 +/- 5.5 ms/mmHg) and increasing MAP (9.6 +/- 2.1 to 9.9 +/- 2.2 ms/mmHg) and the peripheral sympathetic baroslope (-3.3 +/- 0.4 to -3.5 +/- 0.6 bursts.min-1 x mmHg-1) did not differ. The results suggest that short-term aerobic training does not alter resting MSNA or neurocirculatory responses to baroreceptor challenges in middle-aged and older men.

Effect of head-out water immersion on response to exercise training.

During spaceflight and head-out water immersion (WI) there is a cephalad shift in blood volume. We have recently shown that left ventricular end-diastolic dimension is significantly greater during moderate cycling exercise with WI compared with on land. The purpose of this study was to determine whether the cephalad shift in blood volume and accompanying increase in cardiac preload with WI alters the normal cardiovascular adaptations to aerobic exercise training. Nine middle-aged healthy men trained on cycle ergometers in water, nine trained on land, and four served as controls for 12 wk. Following training, both training groups showed similar increase (P less than 0.05) in stroke volume and similar decreases in heart rate (P less than 0.01) and blood pressure (P less than 0.05) at a given submaximal exercise O2 consumption (VO2). Maximal VO2 increased (P less than 0.01) similarly for both training groups. The control group did not demonstrate any significant changes in submaximal or maximal exercise responses. We conclude that the cephalad shift in blood volume with WI does not alter the normal cardiovascular adaptation to aerobic exercise training.

Effect of increased central blood volume with water immersion on plasma catecholamines during exercise.

To examine the influence of an increase in central blood volume with head-out water immersion (WI) on the sympathoadrenal response to graded dynamic exercise, nine healthy men underwent upright leg cycle exercise on land and with WI. Plasma norepinephrine and epinephrine concentrations were used as indexes of overall sympathoadrenal activity. Oxygen consumption (VO2), heart rate, systolic blood pressure, and plasma concentrations of norepinephrine, epinephrine, and lactate were determined at work loads corresponding to approximately 40, 60, 80, and 100% peak VO2. Peak VO2 did not differ on land and with WI. Plasma norepinephrine concentration was reduced (P less than 0.05) at 80 and 100% peak VO2 with WI and on land, respectively. Plasma epinephrine and lactate concentrations were similar on land and with WI at the three submaximal work stages, but both were reduced (P less than 0.05) at peak exertion with WI. Heart rate was lower (P less than 0.05) at the three highest work intensities with WI. These results suggest that the central shift in blood volume with WI reduces the sympathoadrenal response to high-intensity dynamic exercise.