Effect Of Isometric Exercise Research Articles

Effect of isometric exercise on cardiac performance and mitral regurgitation in patients with severe congestive heart failure

Left ventricular performance was studied during isometric exercise in 17 patients with severe congestive heart failure, combining invasive hemodynamic and echo-Doppler techniques. Isometric exercise at 30% of maximum resulted in a decrease in stroke volume index (27.4 ± 7.1 to 22.7 ± 7.4 ml/m 2), with a significant increase in heart rate from 81 ± 10 to 92 ± 14 beats/min and in systemic vascular resistance from 1827 ± 527 to 2372 ± 737 dyne · sec · cm −5. A significant rise in pulmonary capillary wedge pressure (18 ± 9 to 31 ± 10 mm Hg) was associated with a marked increase in mitral regurgitant volume (14 ± 11 to 27 ± 15 ml), calculated as the difference between total stroke volume obtained by two-dimensional echocardiography and forward stroke volume measured by pulsed Doppler at the aortic anulus. During isometric exercise, left ventricular end-diastolic and end-systolic volumes did not change markedly, but the total stroke volume tended to increase from 62 ± 13 to 67 ± 13 ml. The increase in mitral regurgitant volume induced by isometric exercise was correlated with the fall in forward stroke volume ( r = 0.7, p < 0.01). Thus a rise in systemic arterial pressure induced by isometric exercise is associated with a decrease in cardiac performance attributable to redistribution of total left ventricular output with an increase in mitral regurgitation and a simultaneous decrease in forward cardiac output.

Effects of isometric exercise and heart rate on left ventricular filling pattern assessed by pulsed Doppler echocardiography.

Left ventricular filling pattern was assessed by pulsed Doppler echocardiography at rest and during handgrip exercise in 33 healthy middle-aged subjects. The peak mitral flow-velocities during the early rapid filling phase (E) and during late (atrial) filling (A) were measured and the ratio of these peak flow-velocities (E:A ratio) was calculated. The E:A ratio was inversely related to age (r = -0.50), heart rate (r = -0.47) and septal thickness (r = -0.36) at rest. Exercise caused a significant (P less than 0.001) decrease in E:A ratio as a result of an increase in the peak A velocity. No significant change in the peak E velocity was observed during exercise. The exercise E:A ratio was related to heart rate (r = -0.53), but not to resting E:A ratio or age, since the decrease in E:A ratio tended to be less in the older subjects. Our study shows that isometric exercise augments the relative contribution of atrial contraction of left ventricular filling and this increase may 'mask' minor changes in resting transmitral flow pattern associated with, e.g. ageing. Secondly, in addition to age, heart rate must be taken into account when studying populations with different heart-rate levels or interventions associated with simultaneous heart rate changes.

Effects of Isometric Exercise on Blood Cell Adrenoceptors in Essential Hypertension

The effect of handgrip (HG) isometric exercise on plasma catecholamines, alpha 2-adrenoceptors on platelets and beta 2-adrenoceptors on lymphocytes was studied in normotensive subjects (NT) and essential hypertensive subjects (HT). Whereas systolic blood pressure (SBP) increases were similar in NT and HT subjects, diastolic blood pressure (DBP) and heart rate (HR) increased more in the former group. Baseline values and changes in plasma epinephrine (E) and norepinephrine (NE) did not differ between both groups. No differences were apparent in alpha 2-adrenoceptor density and affinity between NT and HT subjects before or after the test. HG isometric exercise induced a similar increase in beta 2-adrenoceptors on lymphocytes of 22 +/- 7 and 13 +/- 5% in NT and HT subjects, respectively. Affinity to the beta 2-adrenoceptors under baseline conditions was somewhat lower in HT (8.1 +/- 0.4 pM) than in NT subjects (6.5 +/- 0.5 pM), and this difference persisted during the test. Our results indicate that there are no differences in alpha 2- and beta 2-adrenoceptor densities either at baseline conditions or after HG isometric exercise between NT and HT subjects. Small differences noted in affinity to the beta 2-adrenoceptors require further investigation.

Regional left ventricular mechanical function during isometric exercise in patients with coronary artery disease: Correlation with regional coronary blood flow changes

The effects of isometric exercise on regional left ventricular mechanical function and regional coronary blood flow were evaluated in 17 patients with significant proximal stenosis of the left anterior descending coronary artery and 10 patients with normal coronary arteriograms. All patients had normal myocardial contractility in the basal condition. All performed isometric handgrip exercise at 50% of the maximal voluntary contraction for 3 min during two-dimensional echocardiographic monitoring and hemodynamic evaluation of great cardiac vein flow by thermodilution technique.During isometric exercise, 7 of the 17 patients with left anterior descending coronary stenosis developed asynergy in the anterior territory (anterior or septal segment, or both) (group I); the remaining 10 showed normal myocardial contraction during the test (group II). The 10 normal subjects manifested no regional asynergy during the test (control group). The increase in great cardiac vein flow at peak isometric exercise was significantly smaller (p < 0.01) in group I (+15 ± 8%) than that in group II (+98 ± 48%) and the control group (+64 ± 22%). Anterior coronaryvascular resistance decreased in group II (−32 ± 13%) and in the control group (−25 ± 8%) bus increased in group I (+6 ± 8%, p < 0.01 versus group II and control group).These data demonstrate that handgrip-induced myocardial asynergy is associated, in our study patients, with an abnormal response of the regional coronary circulation. The increase in coronary vascular resistance in group I patients with asynergy demonstrates that functional mechanisms play a dominant role in left ventricular mechanical dysfunction induced by isometric exercise.

Muscle blood flow during isometric activity and its relation to muscle fatigue.

The effect of isometric exercise on blood flow, blood pressure, intramuscular pressure as well as lactate and potassium efflux from exercising muscle was examined. The contractions performed were continuous or intermittent (5 s on, 5 s off) and varied between 5% and 50% maximal voluntary contraction (MVC). A knee-extensor and a hand-grip protocol were used. Evidence is presented that blood flow through the muscle is sufficient during low-level sustained contractions (less than 10% MVC). Despite this muscle fatigue occurs during prolonged contractions. One mechanism for this fatigue may be the disturbance of the potassium homeostasis. Such changes may also play a role in the development of fatigue during intermittent isometric contractions and even more so in the recovery from such exercise. In addition the role of impaired transport of substances within the muscle, due to long-lasting daily oedema formation, is discussed in relation to fatigue in highly repetitive, monotonous jobs.

Effects of isometric exercise on blood coagulability and platelet functions

Effects of isometric exercise on blood coagulability and platelet functions

Isometric Exercise Testing

In the past decade, a great deal of interest has been focused on the hemodynamic effects of isometric exercise, a form of exercise where the contracting muscles develop force without shortening. Although certain details remain to be clarified, the existing body of knowledge indicates that isometric exercise has pronounced positive chronotropic, inotropic, and pressor effects on the cardiovascular system, and the magnitude and nature of the hemodynamic response of the normal heart to isometric exercise are different from those observed in the presence of heart disease. These facts, and the ease with which graded isometric exercise can be performed by use of a small instrument (dynamometer) that is manually squeezed by the patient (isometric handgrip test), have led to further studies directed at three potentially rewarding clinical applications of the test. The first diagnostic use of the isometric exercise test is for the detection of latent left ventricular (LV) failure.

Effects of isometric exercise on the carotid baroreflex in hypertensive subjects.

Previous studies indicate that arterial baroreceptor modulation of heart rate is drastically reduced during static or dynamic exercise. We have investigated whether this reduction also occurs with regard to blood pressure modulation by the baroreflex. The study was performed in 19 subjects with uncomplicated untreated essential hypertension in whom blood pressure was measured intraarterially, and R-R interval was obtained by an electrocardiogram. The carotid baroreceptors were stimulated by neck suction of 30 seconds' duration, and equal stimuli were applied at rest and during hand-grip exercise performed at 40% of the subjects' maximal strength. Baroreceptor stimulation at rest increased R-R interval and reduced blood pressure. During hand-grip, the R-R interval responses to the baroreceptor stimulus were diminished by 61%. In contrast, the blood pressure responses were not significantly altered. Similar results were obtained when two subgroups of subjects with a lesser or greater degree of hypertension were separately considered. Thus, the carotid baroreceptor influence on blood pressure is largely preserved during exercise in contrast to the carotid baroreceptor influence on the sinus node, which is markedly impaired.

Plasma epinephrine disturbances in diabetic subjects during standing and after isometric exercise.

Effects of isometric exercise on plasma norepinephrine (NE), epinephrine (E), and related factors (mean +/- SE) were studied in 10 healthy, insulin-dependent diabetic subjects and 10 matched control adults. Measurements were obtained after 30 min of bedrest and sequentially during 10 min of upright posture and 5 min of handgrip and after 15 min of rest while still upright. In control and diabetic groups, respectively, basal plasma NE (180 +/- 22 vs. 169 +/- 27 pg/ml) and E (24 +/- 4 vs. 33 +/- 8 pg/ml) as well as heart rate and mean blood pressure did not differ. However, E responses to standing and recovery from isometric exercise in diabetic subjects significantly exceeded control values 2-fold (P less than 0.05) and were accompanied by exaggerated increases in heart rate (P less than 0.05); whereas NE, mean blood pressure, plasma GH, and glucagon profiles during all periods were not significantly different. Exaggerated E responses in diabetic patients were associated with plasma glucose increments above resting values during grip and recovery of 21 and 41 mg/dl, respectively; slightly though significantly higher plasma cortisol responses, and low, fixed concentrations of plasma insulin. These findings contrasted to corresponding glucose increments in control subjects of only 3-4 mg/dl and a 2-fold rise in plasma insulin during recovery. It is concluded that E disturbances in this diabetic group after standing and isometric exercise are physiologically linked to abnormal increments in heart rate and plasma glucose concentrations. These observations suggest that altered E, as opposed to NE, may represent an early defect of the sympathoadrenal system in diabetes mellitus.

Noninvasive Assessment of Changes in Left Ventricular Function Induced by Graded Isometric Exercise in Healthy subjects

This study was designed to characterize the changes in left ventricular performance induced by graded isometric exercise. Fourteen healthy subjects (12 men and 2 women), aged 19 to 27, performed handgrip isometric exercise at 20, 40, and 60 percent of their maximal voluntary contraction (MVC) with three minutes of rest interval between each contraction. Left ventricular performance was assessed by M-mode echocardiography at rest and during each isometric contraction. Left ventricular end-diastolic and end-systolic dimensions did not change significantly. Heart rate and blood pressure increased significantly during each level of isometric contraction. Left ventricular posterior wall thickness fell from 8.6 +/- .4 (mean +/- SE) to 7.1 +/- .5 (P less than 0.01) and 6.5 +/- .4 mm (P less than 0.001) in response to 40 and 60 percent of MVC, respectively. Left ventricular wall thickness to radius ratio decreased progressively as systolic blood pressure increased which suggests increased wall tension. Fractional shortening remained unchanged during graded isometric exercise. However, mean velocity of circumferential fiber shortening (mVcf) increased from 1.08 +/- 0.4 to 1.24 +/- .05 circ/sec (P less than 0.005) in response to 60 percent of MVC. We conclude that the effect of isometric exercise on left ventricular performance depends, to some extent, on the relative strength of muscle contraction. In healthy subjects, isometric exercise of low intensity (less 40 percent of MVC) does not generally result in depression of left ventricular function. Higher levels of isometric exercise may modestly enhance left ventricular performance despite a sudden increase in blood pressure.

Effect of isometric exercise on the renal excretion of sodium and potassium in mild hypertension.

1. Basal levels of pulse rate, blood pressure and rates of sodium and potassium excretion were observed in eight white male patients with mild hypertension and eight age-, sex- and colour-matched controls during an initial rest period of 90 min and then for 5 h after a 1 h period of isometric exercise involving all four limbs in rotation. The studies were repeated on another day with the subjects resting instead of exercising for 1 h. 2. Changes in systolic pressure after exercise were similar in the hypertensive and control groups, whereas the rise in diastolic pressure was higher and the rise in pulse rate lower after exercise in the hypertensive group compared with the control group. 3. The changes in the rate of salt excretion were significantly different in the two groups, the hypertensive group retaining proportionately more sodium and potassium over several hours.

Effect of isometric exercises on body potassium and dietary protein requirements of young men

A diet supplying 0.5 or 1 g egg and milk protein/kg per day and adequate energy for maintenance of body weight was given to seven healthy men aged 18 to 21. After 2 weeks for adaptation to the diet they participated in 75 min of daily isometric exercises for 4 to 6 weeks. Two men on each protein intake continued to exercise for 4 to 5 additional weeks after undergoing changes in their daily protein intake from 0.5 to 1 g/kg or vice versa. A progressive decrease in total body potassium became significant by the fourth week of exercises in all men who began on the 0.5 g protein diet. Two men on that diet who remained as nonexercising controls lost no body K. These findings indicated that 0.5 g of egg and milk protein/kg per day was insufficient for men performing isometric exercises without prior training, whereas 1 g/kg per day appeared to be adequate. Two other nonexercising men on the 0.5 g diet who lost weight showed a marked negative nitrogen balance and loss of total body potassium which improved after their dietary energy intake increased. The changes in nitrogen balance and body weight observed in this investigation support the concept that protein requirements vary with energy intakes. Conversely, they suggest that energy requirements are influenced by the level of protein intake.

Effects of isometric exercise and increased arterial impedance on left ventricular function in severe aortic valvular stenosis.

Effects of isometric exercise and increased arterial impedance on left ventricular function in severe aortic valvular stenosis.

Effect of isometric exercise on catecholamines in the coronary circulation

Arterial and coronary sinus blood levels of catecholamines, adenosine 3', 5'-cyclic monophosphate (c-AMP) and lactate were measured during isometric exercise in fourteen patients. In no patient did lactate production occur. Mean resting total catecholamine levels both arterial (0.53 +/- 0.07 ng/ml; 2.94 +/- 0.38 nmol/l) and coronary sinus (0.4 +/- 0.08 ng/ml; 2.22 +/- 0.44 nmol/l), did not change significantly on exercise. Coronary sinus c-AMP levels fell on exercise from 11.5 +/- 0.8 nmol/l (resting) to 9.9 +/- 0.8 nmol/l (exercise) (P less than 0.01) with an arterial-coronary sinus difference of 1.2 nmol/l (P less than 0.01) on exercise. Our findings suggest that isometric exercise does not normally result in excessive cardiac symphathetic activity.

Effects of isometric exercise on serum creatine phosphokinase activity.

The effect of isometric exercise on serum creatinine phosphokinase (CPK) activity in 14 psychotic patients in remission and ten normal controls was studied. The increases in serum CPK activity at 18 and 42 hours after exercise were no significantly different in patients and controls. The postexercise serum CPK activities in the patients were significantly less than the peak serum CPK levels when they were psychotic. There were no significant correlations between postexercise serum CPK activity and preexercise or peak serum CPK activity in the patient group. It is unlikely that increased isometric muscle tension is a major causative factor in the increased serum CPK levels frequently found in psychotic patients.

Effects of isometric exercise on the end-diastolic pressure, volumes, and function of the left ventricle in man.

Changes induced in left ventricular (LV) hemodynamics by isometric exercise were analyzed in 43 patients: 30 with coronary heart disease (CAD), four with noncoronary heart disease, nine normal. Volumes were angiographically determined and correlated with left ventricular end-diastolic pressure (LVEDP) both at rest and during the fifth minute of 30% sustained handgrip (HNG). All normals and eight with CAD improved LV function during HNG. LVEDP decreased or remained constant, end-diastolic volume (EDV) decreased, end-systolic volume (ESV) decreased, as ejection fraction (EF) remained constant. None of these eight CAD cases altered their regional LV contraction pattern during HNG. Twenty-five patients, 21 CAD and four nonCAD, showed diminished LV function during HNG. LVEDP increased, EDV decreased, ESV increased, as EF declined. In these 21 CAD patients, at least one major coronary vessel was narrowed 70% or more and, with but two exceptions, was not supported by adequate collaterals. In 18, new asynergic zones developed in previously normally contracting areas or pre-existing asynergic zones extended during HNG.

The Effect of Isometric Exercise on the Systolic Murmur of Patients with Idiopathic Hypertrophic Subaortic Stenosis

The effect of isometric handgrip exercise on the systolic murmur and bifid pulse in patients with idiopathic hypertrophic subaortic stenosis (IHSS) was evaluated. During handgrip exercise, the systolic murmur became inaudible or decreased in intensity by auscultation and disappeared or decreased in amplitude in phonocardiographic recordings in nine of nine patients with IHSS. During handgrip exercise, the bifid pulse observed in seven patients with IHSS disappeared or markedly decreased. Handgrip exercise may be helpful in the bedside diagnosis of IHSS.

Left ventricular function in mitral stenosis.

The effects of isometric exercise on left ventricular performance were studied during cardiac catheterization in six patients with mitral stenosis and six patients without significant cardiac disease. Quantitative analyses of left ventricular cineangiograms were completed to correlate changes with the findings during exercise. During exercise, left ventricular function curves were abnormal in five of the six patients with mitral stenosis. In addition, ejection fractions were significantly lower in the group with mitral stenosis as compared with the normal subjects. The lower ejection fractions in the patients with mitral stenosis were due to localized abnormalities in the posterobasal and anterior left ventricular walls. It is concluded that left ventricular function is abnormal in mitral stenosis due to localized wall motion abnormalities, which are probably due to fibrosis near or in the papillary muscles.

Isometric training of rats--effects upon fast and slow muscle and modification by an anabolic hormone (nandrolone decanoate). II. Male rats.

Some effects of isometric exercise were studied in fast rectus femoris muscle and slow soleus muscle of the male rat. Isometric twitch contraction time did not change in both muscles, however, maximum tetanic tension increased in the fast muscle. Changes in the enzyme activity pattern of energy supplying metabolism of the rectus femoris muscle consisted in an increase of creatine kinase and citrate synthetase and a decrease of mitochondrial glycerolphosphate dehydrogenase. Treatment with Nandrolone Decanoate caused much smaller changes in male than observed in the preceding study on female rats. There was a higher performance of the trained animals under the influence of the hormone, but no changes could be found in the activities of the investigated enzymes. Combination of training with hormone treatment led to no further increase of maximal tetanic tension of the rectus femoris. Training and hormone treatment together caused an increase in glycogen phosphorylase and prevented partially the decrease in mitochondrial glycerolphosphate dehydrogenase observed under training alone. Some of the changes seen in the rectus femoris muscle after training were comparable to those in the female rats. Neither training nor hormone treatment induced changes in the male soleus muscle, except for the increase of soluble protein in sedentary hormone treated animals.

Effects of isometric exercise on cardiac performance. The grip test.

Twenty-two patients with heart disease performed a standard isometric exercise, sustained handgrip, during the course of diagnostic cardiac catheterization. During handgrip an increase in mean arterial pressure (average 87 to 104 mm Hg) was noted in all patients. Coronary sinus blood flow and myocardial O 2 consumption increased (average 45%) in all patients so monitored. Systemic vascular resistance increased in 19 patients, in contrast to the response reported in normal volunteers. The relation between left ventricular stroke-work index and LVEDP (left ventricular function curve) during the control state and during the fourth minute of sustained handgrip provided a simple estimate of left ventricular reserve and correlated well with the New York Heart Association functional classification of the patient studied. Patients with good reserve had a rise in stroke-work with little or no change in LVEDP. Patients with poor reserve had a fall in stroke-work together with a substantial rise in LVEDP. It is concluded that the stress imposed by sustained handgrip provides a simple test for the evaluation of left ventricular reserve.